{"api_version":"1","generated_at":"2026-04-23T06:21:14+00:00","cve":"CVE-2026-23198","urls":{"html":"https://cve.report/CVE-2026-23198","api":"https://cve.report/api/cve/CVE-2026-23198.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-23198","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-23198"},"summary":{"title":"KVM: Don't clobber irqfd routing type when deassigning irqfd","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: Don't clobber irqfd routing type when deassigning irqfd\n\nWhen deassigning a KVM_IRQFD, don't clobber the irqfd's copy of the IRQ's\nrouting entry as doing so breaks kvm_arch_irq_bypass_del_producer() on x86\nand arm64, which explicitly look for KVM_IRQ_ROUTING_MSI.  Instead, to\nhandle a concurrent routing update, verify that the irqfd is still active\nbefore consuming the routing information.  As evidenced by the x86 and\narm64 bugs, and another bug in kvm_arch_update_irqfd_routing() (see below),\nclobbering the entry type without notifying arch code is surprising and\nerror prone.\n\nAs a bonus, checking that the irqfd is active provides a convenient\nlocation for documenting _why_ KVM must not consume the routing entry for\nan irqfd that is in the process of being deassigned: once the irqfd is\ndeleted from the list (which happens *before* the eventfd is detached), it\nwill no longer receive updates via kvm_irq_routing_update(), and so KVM\ncould deliver an event using stale routing information (relative to\nKVM_SET_GSI_ROUTING returning to userspace).\n\nAs an even better bonus, explicitly checking for the irqfd being active\nfixes a similar bug to the one the clobbering is trying to prevent: if an\nirqfd is deactivated, and then its routing is changed,\nkvm_irq_routing_update() won't invoke kvm_arch_update_irqfd_routing()\n(because the irqfd isn't in the list).  And so if the irqfd is in bypass\nmode, IRQs will continue to be posted using the old routing information.\n\nAs for kvm_arch_irq_bypass_del_producer(), clobbering the routing type\nresults in KVM incorrectly keeping the IRQ in bypass mode, which is\nespecially problematic on AMD as KVM tracks IRQs that are being posted to\na vCPU in a list whose lifetime is tied to the irqfd.\n\nWithout the help of KASAN to detect use-after-free, the most common\nsympton on AMD is a NULL pointer deref in amd_iommu_update_ga() due to\nthe memory for irqfd structure being re-allocated and zeroed, resulting\nin irqfd->irq_bypass_data being NULL when read by\navic_update_iommu_vcpu_affinity():\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000018\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 40cf2b9067 P4D 40cf2b9067 PUD 408362a067 PMD 0\n  Oops: Oops: 0000 [#1] SMP\n  CPU: 6 UID: 0 PID: 40383 Comm: vfio_irq_test\n  Tainted: G     U  W  O        6.19.0-smp--5dddc257e6b2-irqfd #31 NONE\n  Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE\n  Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025\n  RIP: 0010:amd_iommu_update_ga+0x19/0xe0\n  Call Trace:\n   <TASK>\n   avic_update_iommu_vcpu_affinity+0x3d/0x90 [kvm_amd]\n   __avic_vcpu_load+0xf4/0x130 [kvm_amd]\n   kvm_arch_vcpu_load+0x89/0x210 [kvm]\n   vcpu_load+0x30/0x40 [kvm]\n   kvm_arch_vcpu_ioctl_run+0x45/0x620 [kvm]\n   kvm_vcpu_ioctl+0x571/0x6a0 [kvm]\n   __se_sys_ioctl+0x6d/0xb0\n   do_syscall_64+0x6f/0x9d0\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x46893b\n    </TASK>\n  ---[ end trace 0000000000000000 ]---\n\nIf AVIC is inhibited when the irfd is deassigned, the bug will manifest as\nlist corruption, e.g. on the next irqfd assignment.\n\n  list_add corruption. next->prev should be prev (ffff8d474d5cd588),\n                       but was 0000000000000000. (next=ffff8d8658f86530).\n  ------------[ cut here ]------------\n  kernel BUG at lib/list_debug.c:31!\n  Oops: invalid opcode: 0000 [#1] SMP\n  CPU: 128 UID: 0 PID: 80818 Comm: vfio_irq_test\n  Tainted: G     U  W  O        6.19.0-smp--f19dc4d680ba-irqfd #28 NONE\n  Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE\n  Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025\n  RIP: 0010:__list_add_valid_or_report+0x97/0xc0\n  Call Trace:\n   <TASK>\n   avic_pi_update_irte+0x28e/0x2b0 [kvm_amd]\n   kvm_pi_update_irte+0xbf/0x190 [kvm]\n   kvm_arch_irq_bypass_add_producer+0x72/0x90 [kvm]\n   irq_bypass_register_consumer+0xcd/0x170 [irqbypa\n---truncated---","state":"PUBLISHED","assigner":"Linux","published_at":"2026-02-14 17:15:57","updated_at":"2026-04-03 14:16:27"},"problem_types":["CWE-476"],"metrics":[{"version":"3.1","source":"nvd@nist.gov","type":"Primary","score":"5.5","severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","baseScore":5.5,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"}},{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/2284bc168b148a17b5ca3b37b3d95c411f18a08d","name":"https://git.kernel.org/stable/c/2284bc168b148a17b5ca3b37b3d95c411f18a08d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4385b2f2843549bfb932e0dcf76bf4b065543a3c","name":"https://git.kernel.org/stable/c/4385b2f2843549bfb932e0dcf76bf4b065543a3c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/959a063e7f12524bc1871ad1f519787967bbcd45","name":"https://git.kernel.org/stable/c/959a063e7f12524bc1871ad1f519787967bbcd45","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/6d14ba1e144e796b5fc81044f08cfba9024ca195","name":"https://git.kernel.org/stable/c/6d14ba1e144e796b5fc81044f08cfba9024ca195","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b4d37cdb77a0015f51fee083598fa227cc07aaf1","name":"https://git.kernel.org/stable/c/b4d37cdb77a0015f51fee083598fa227cc07aaf1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ff48c9312d042bfbe826ca675e98acc6c623211c","name":"https://git.kernel.org/stable/c/ff48c9312d042bfbe826ca675e98acc6c623211c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b61f9b2fcf181451d0a319889478cc53c001123e","name":"https://git.kernel.org/stable/c/b61f9b2fcf181451d0a319889478cc53c001123e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-23198","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23198","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f70c20aaf141adb715a2d750c55154073b02a9c3 959a063e7f12524bc1871ad1f519787967bbcd45 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f70c20aaf141adb715a2d750c55154073b02a9c3 2284bc168b148a17b5ca3b37b3d95c411f18a08d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f70c20aaf141adb715a2d750c55154073b02a9c3 6d14ba1e144e796b5fc81044f08cfba9024ca195 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f70c20aaf141adb715a2d750c55154073b02a9c3 b61f9b2fcf181451d0a319889478cc53c001123e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f70c20aaf141adb715a2d750c55154073b02a9c3 ff48c9312d042bfbe826ca675e98acc6c623211c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f70c20aaf141adb715a2d750c55154073b02a9c3 4385b2f2843549bfb932e0dcf76bf4b065543a3c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f70c20aaf141adb715a2d750c55154073b02a9c3 b4d37cdb77a0015f51fee083598fa227cc07aaf1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.4","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 4.4 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.10.250 5.10.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.200 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.163 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.124 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.70 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.10 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[{"cve_year":"2026","cve_id":"23198","vulnerable":"1","versionEndIncluding":"","cpe1":"cpe","cpe2":"2.3","cpe3":"o","cpe4":"linux","cpe5":"linux_kernel","cpe6":"*","cpe7":"*","cpe8":"*","cpe9":"*","cpe10":"*","cpe11":"*","cpe12":"*","cpe13":"*"}],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["virt/kvm/eventfd.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"959a063e7f12524bc1871ad1f519787967bbcd45","status":"affected","version":"f70c20aaf141adb715a2d750c55154073b02a9c3","versionType":"git"},{"lessThan":"2284bc168b148a17b5ca3b37b3d95c411f18a08d","status":"affected","version":"f70c20aaf141adb715a2d750c55154073b02a9c3","versionType":"git"},{"lessThan":"6d14ba1e144e796b5fc81044f08cfba9024ca195","status":"affected","version":"f70c20aaf141adb715a2d750c55154073b02a9c3","versionType":"git"},{"lessThan":"b61f9b2fcf181451d0a319889478cc53c001123e","status":"affected","version":"f70c20aaf141adb715a2d750c55154073b02a9c3","versionType":"git"},{"lessThan":"ff48c9312d042bfbe826ca675e98acc6c623211c","status":"affected","version":"f70c20aaf141adb715a2d750c55154073b02a9c3","versionType":"git"},{"lessThan":"4385b2f2843549bfb932e0dcf76bf4b065543a3c","status":"affected","version":"f70c20aaf141adb715a2d750c55154073b02a9c3","versionType":"git"},{"lessThan":"b4d37cdb77a0015f51fee083598fa227cc07aaf1","status":"affected","version":"f70c20aaf141adb715a2d750c55154073b02a9c3","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["virt/kvm/eventfd.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"4.4"},{"lessThan":"4.4","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.250","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.200","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.163","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.124","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.70","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.10","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"6.19","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.250","versionStartIncluding":"4.4","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.200","versionStartIncluding":"4.4","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.163","versionStartIncluding":"4.4","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.124","versionStartIncluding":"4.4","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.70","versionStartIncluding":"4.4","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.10","versionStartIncluding":"4.4","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.19","versionStartIncluding":"4.4","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: Don't clobber irqfd routing type when deassigning irqfd\n\nWhen deassigning a KVM_IRQFD, don't clobber the irqfd's copy of the IRQ's\nrouting entry as doing so breaks kvm_arch_irq_bypass_del_producer() on x86\nand arm64, which explicitly look for KVM_IRQ_ROUTING_MSI.  Instead, to\nhandle a concurrent routing update, verify that the irqfd is still active\nbefore consuming the routing information.  As evidenced by the x86 and\narm64 bugs, and another bug in kvm_arch_update_irqfd_routing() (see below),\nclobbering the entry type without notifying arch code is surprising and\nerror prone.\n\nAs a bonus, checking that the irqfd is active provides a convenient\nlocation for documenting _why_ KVM must not consume the routing entry for\nan irqfd that is in the process of being deassigned: once the irqfd is\ndeleted from the list (which happens *before* the eventfd is detached), it\nwill no longer receive updates via kvm_irq_routing_update(), and so KVM\ncould deliver an event using stale routing information (relative to\nKVM_SET_GSI_ROUTING returning to userspace).\n\nAs an even better bonus, explicitly checking for the irqfd being active\nfixes a similar bug to the one the clobbering is trying to prevent: if an\nirqfd is deactivated, and then its routing is changed,\nkvm_irq_routing_update() won't invoke kvm_arch_update_irqfd_routing()\n(because the irqfd isn't in the list).  And so if the irqfd is in bypass\nmode, IRQs will continue to be posted using the old routing information.\n\nAs for kvm_arch_irq_bypass_del_producer(), clobbering the routing type\nresults in KVM incorrectly keeping the IRQ in bypass mode, which is\nespecially problematic on AMD as KVM tracks IRQs that are being posted to\na vCPU in a list whose lifetime is tied to the irqfd.\n\nWithout the help of KASAN to detect use-after-free, the most common\nsympton on AMD is a NULL pointer deref in amd_iommu_update_ga() due to\nthe memory for irqfd structure being re-allocated and zeroed, resulting\nin irqfd->irq_bypass_data being NULL when read by\navic_update_iommu_vcpu_affinity():\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000018\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 40cf2b9067 P4D 40cf2b9067 PUD 408362a067 PMD 0\n  Oops: Oops: 0000 [#1] SMP\n  CPU: 6 UID: 0 PID: 40383 Comm: vfio_irq_test\n  Tainted: G     U  W  O        6.19.0-smp--5dddc257e6b2-irqfd #31 NONE\n  Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE\n  Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025\n  RIP: 0010:amd_iommu_update_ga+0x19/0xe0\n  Call Trace:\n   <TASK>\n   avic_update_iommu_vcpu_affinity+0x3d/0x90 [kvm_amd]\n   __avic_vcpu_load+0xf4/0x130 [kvm_amd]\n   kvm_arch_vcpu_load+0x89/0x210 [kvm]\n   vcpu_load+0x30/0x40 [kvm]\n   kvm_arch_vcpu_ioctl_run+0x45/0x620 [kvm]\n   kvm_vcpu_ioctl+0x571/0x6a0 [kvm]\n   __se_sys_ioctl+0x6d/0xb0\n   do_syscall_64+0x6f/0x9d0\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x46893b\n    </TASK>\n  ---[ end trace 0000000000000000 ]---\n\nIf AVIC is inhibited when the irfd is deassigned, the bug will manifest as\nlist corruption, e.g. on the next irqfd assignment.\n\n  list_add corruption. next->prev should be prev (ffff8d474d5cd588),\n                       but was 0000000000000000. (next=ffff8d8658f86530).\n  ------------[ cut here ]------------\n  kernel BUG at lib/list_debug.c:31!\n  Oops: invalid opcode: 0000 [#1] SMP\n  CPU: 128 UID: 0 PID: 80818 Comm: vfio_irq_test\n  Tainted: G     U  W  O        6.19.0-smp--f19dc4d680ba-irqfd #28 NONE\n  Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE\n  Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025\n  RIP: 0010:__list_add_valid_or_report+0x97/0xc0\n  Call Trace:\n   <TASK>\n   avic_pi_update_irte+0x28e/0x2b0 [kvm_amd]\n   kvm_pi_update_irte+0xbf/0x190 [kvm]\n   kvm_arch_irq_bypass_add_producer+0x72/0x90 [kvm]\n   irq_bypass_register_consumer+0xcd/0x170 [irqbypa\n---truncated---"}],"metrics":[{"cvssV3_1":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-04-03T13:32:28.519Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/959a063e7f12524bc1871ad1f519787967bbcd45"},{"url":"https://git.kernel.org/stable/c/2284bc168b148a17b5ca3b37b3d95c411f18a08d"},{"url":"https://git.kernel.org/stable/c/6d14ba1e144e796b5fc81044f08cfba9024ca195"},{"url":"https://git.kernel.org/stable/c/b61f9b2fcf181451d0a319889478cc53c001123e"},{"url":"https://git.kernel.org/stable/c/ff48c9312d042bfbe826ca675e98acc6c623211c"},{"url":"https://git.kernel.org/stable/c/4385b2f2843549bfb932e0dcf76bf4b065543a3c"},{"url":"https://git.kernel.org/stable/c/b4d37cdb77a0015f51fee083598fa227cc07aaf1"}],"title":"KVM: Don't clobber irqfd routing type when deassigning irqfd","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-23198","datePublished":"2026-02-14T16:27:23.621Z","dateReserved":"2026-01-13T15:37:45.985Z","dateUpdated":"2026-04-03T13:32:28.519Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-02-14 17:15:57","lastModifiedDate":"2026-04-03 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Don't clobber irqfd routing type when deassigning irqfd","CVE":"CVE-2026-23198","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"23198","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: Don't clobber irqfd routing type when deassigning irqfd\n\nWhen deassigning a KVM_IRQFD, don't clobber the irqfd's copy of the IRQ's\nrouting entry as doing so breaks kvm_arch_irq_bypass_del_producer() on x86\nand arm64, which explicitly look for KVM_IRQ_ROUTING_MSI.  Instead, to\nhandle a concurrent routing update, verify that the irqfd is still active\nbefore consuming the routing information.  As evidenced by the x86 and\narm64 bugs, and another bug in kvm_arch_update_irqfd_routing() (see below),\nclobbering the entry type without notifying arch code is surprising and\nerror prone.\n\nAs a bonus, checking that the irqfd is active provides a convenient\nlocation for documenting _why_ KVM must not consume the routing entry for\nan irqfd that is in the process of being deassigned: once the irqfd is\ndeleted from the list (which happens *before* the eventfd is detached), it\nwill no longer receive updates via kvm_irq_routing_update(), and so KVM\ncould deliver an event using stale routing information (relative to\nKVM_SET_GSI_ROUTING returning to userspace).\n\nAs an even better bonus, explicitly checking for the irqfd being active\nfixes a similar bug to the one the clobbering is trying to prevent: if an\nirqfd is deactivated, and then its routing is changed,\nkvm_irq_routing_update() won't invoke kvm_arch_update_irqfd_routing()\n(because the irqfd isn't in the list).  And so if the irqfd is in bypass\nmode, IRQs will continue to be posted using the old routing information.\n\nAs for kvm_arch_irq_bypass_del_producer(), clobbering the routing type\nresults in KVM incorrectly keeping the IRQ in bypass mode, which is\nespecially problematic on AMD as KVM tracks IRQs that are being posted to\na vCPU in a list whose lifetime is tied to the irqfd.\n\nWithout the help of KASAN to detect use-after-free, the most common\nsympton on AMD is a NULL pointer deref in amd_iommu_update_ga() due to\nthe memory for irqfd structure being re-allocated and zeroed, resulting\nin irqfd->irq_bypass_data being NULL when read by\navic_update_iommu_vcpu_affinity():\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000018\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 40cf2b9067 P4D 40cf2b9067 PUD 408362a067 PMD 0\n  Oops: Oops: 0000 [#1] SMP\n  CPU: 6 UID: 0 PID: 40383 Comm: vfio_irq_test\n  Tainted: G     U  W  O        6.19.0-smp--5dddc257e6b2-irqfd #31 NONE\n  Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE\n  Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025\n  RIP: 0010:amd_iommu_update_ga+0x19/0xe0\n  Call Trace:\n   <TASK>\n   avic_update_iommu_vcpu_affinity+0x3d/0x90 [kvm_amd]\n   __avic_vcpu_load+0xf4/0x130 [kvm_amd]\n   kvm_arch_vcpu_load+0x89/0x210 [kvm]\n   vcpu_load+0x30/0x40 [kvm]\n   kvm_arch_vcpu_ioctl_run+0x45/0x620 [kvm]\n   kvm_vcpu_ioctl+0x571/0x6a0 [kvm]\n   __se_sys_ioctl+0x6d/0xb0\n   do_syscall_64+0x6f/0x9d0\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x46893b\n    </TASK>\n  ---[ end trace 0000000000000000 ]---\n\nIf AVIC is inhibited when the irfd is deassigned, the bug will manifest as\nlist corruption, e.g. on the next irqfd assignment.\n\n  list_add corruption. next->prev should be prev (ffff8d474d5cd588),\n                       but was 0000000000000000. (next=ffff8d8658f86530).\n  ------------[ cut here ]------------\n  kernel BUG at lib/list_debug.c:31!\n  Oops: invalid opcode: 0000 [#1] SMP\n  CPU: 128 UID: 0 PID: 80818 Comm: vfio_irq_test\n  Tainted: G     U  W  O        6.19.0-smp--f19dc4d680ba-irqfd #28 NONE\n  Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE\n  Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025\n  RIP: 0010:__list_add_valid_or_report+0x97/0xc0\n  Call Trace:\n   <TASK>\n   avic_pi_update_irte+0x28e/0x2b0 [kvm_amd]\n   kvm_pi_update_irte+0xbf/0x190 [kvm]\n   kvm_arch_irq_bypass_add_producer+0x72/0x90 [kvm]\n   irq_bypass_register_consumer+0xcd/0x170 [irqbypa\n---truncated---","Type":"Description","Title":"KVM: Don't clobber irqfd routing type when deassigning irqfd"}]}}}