{"api_version":"1","generated_at":"2026-09-17T08:30:32+00:00","cve":"CVE-2026-89902","urls":{"html":"https://cve.report/CVE-2026-89902","api":"https://cve.report/api/cve/CVE-2026-89902.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89902","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89902"},"summary":{"title":"LoongArch: Avoid preempt count underflow without probe","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nLoongArch: Avoid preempt count underflow without probe\n\nLoongArch uses break 11 for the breakpoint placed after an instruction\nthat Kprobes executes out of line. Since userspace can issue the same\nbreak instruction, do_bp() can reach kprobe_singlestep_handler() when\nthere is no current probe.\n\nThe handler actually returns false in this case, but it first calls\npreempt_enable_no_resched(). The corresponding preempt_disable() is done\nby kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run\nhere. As a result, an ordinary userspace breakpoint (code 11) underflows\nthe current task's preempt count.\n\nThis also makes in_interrupt() return true until the task schedules. One\nvisible consequence is the socket cgroup attribution: cgroup_sk_alloc()\ntreats the allocation as interrupt context and assigns the socket to the\nroot cgroup. A socket opened from the SIGTRAP handler can then avoid a\nBPF_CGROUP_INET_SOCK_CREATE policy attached to the task's own cgroup.\n\nReturn as soon as kprobe_running() reports no active probe.\n\nThe same check has appeared in [PATCH v10 2/4] of the original LoongArch\nKprobes series, but was dropped before the feature reached mainline.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-16 11:16:59","updated_at":"2026-09-16 15:18:16"},"problem_types":[],"metrics":[{"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/72ce4b24676e8b3b75376c4c559dd81c1ac52d5a","name":"https://git.kernel.org/stable/c/72ce4b24676e8b3b75376c4c559dd81c1ac52d5a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ff40e597d5d98c0c45a4d09df8177202fac9520e","name":"https://git.kernel.org/stable/c/ff40e597d5d98c0c45a4d09df8177202fac9520e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c4357ebeee63cb8da1446fc936573a34e68b0f71","name":"https://git.kernel.org/stable/c/c4357ebeee63cb8da1446fc936573a34e68b0f71","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/76395109a051b53860faaec96522ef08ae9e8e27","name":"https://git.kernel.org/stable/c/76395109a051b53860faaec96522ef08ae9e8e27","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a1cb727fa27c2d9c7859729cd90db7bc0f46957f","name":"https://git.kernel.org/stable/c/a1cb727fa27c2d9c7859729cd90db7bc0f46957f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89902","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89902","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6d4cc40fb5f58147defc6c0e9d86e6232fe31616 ff40e597d5d98c0c45a4d09df8177202fac9520e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6d4cc40fb5f58147defc6c0e9d86e6232fe31616 a1cb727fa27c2d9c7859729cd90db7bc0f46957f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6d4cc40fb5f58147defc6c0e9d86e6232fe31616 76395109a051b53860faaec96522ef08ae9e8e27 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6d4cc40fb5f58147defc6c0e9d86e6232fe31616 c4357ebeee63cb8da1446fc936573a34e68b0f71 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6d4cc40fb5f58147defc6c0e9d86e6232fe31616 72ce4b24676e8b3b75376c4c559dd81c1ac52d5a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.3","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.3 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.157 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.110 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.51 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.5 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc2 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["arch/loongarch/kernel/kprobes.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"ff40e597d5d98c0c45a4d09df8177202fac9520e","status":"affected","version":"6d4cc40fb5f58147defc6c0e9d86e6232fe31616","versionType":"git"},{"lessThan":"a1cb727fa27c2d9c7859729cd90db7bc0f46957f","status":"affected","version":"6d4cc40fb5f58147defc6c0e9d86e6232fe31616","versionType":"git"},{"lessThan":"76395109a051b53860faaec96522ef08ae9e8e27","status":"affected","version":"6d4cc40fb5f58147defc6c0e9d86e6232fe31616","versionType":"git"},{"lessThan":"c4357ebeee63cb8da1446fc936573a34e68b0f71","status":"affected","version":"6d4cc40fb5f58147defc6c0e9d86e6232fe31616","versionType":"git"},{"lessThan":"72ce4b24676e8b3b75376c4c559dd81c1ac52d5a","status":"affected","version":"6d4cc40fb5f58147defc6c0e9d86e6232fe31616","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["arch/loongarch/kernel/kprobes.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.3"},{"lessThan":"6.3","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.157","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.110","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.51","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.5","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc2","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.157","versionStartIncluding":"6.3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.110","versionStartIncluding":"6.3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.51","versionStartIncluding":"6.3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.5","versionStartIncluding":"6.3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc2","versionStartIncluding":"6.3","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nLoongArch: Avoid preempt count underflow without probe\n\nLoongArch uses break 11 for the breakpoint placed after an instruction\nthat Kprobes executes out of line. Since userspace can issue the same\nbreak instruction, do_bp() can reach kprobe_singlestep_handler() when\nthere is no current probe.\n\nThe handler actually returns false in this case, but it first calls\npreempt_enable_no_resched(). The corresponding preempt_disable() is done\nby kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run\nhere. As a result, an ordinary userspace breakpoint (code 11) underflows\nthe current task's preempt count.\n\nThis also makes in_interrupt() return true until the task schedules. One\nvisible consequence is the socket cgroup attribution: cgroup_sk_alloc()\ntreats the allocation as interrupt context and assigns the socket to the\nroot cgroup. A socket opened from the SIGTRAP handler can then avoid a\nBPF_CGROUP_INET_SOCK_CREATE policy attached to the task's own cgroup.\n\nReturn as soon as kprobe_running() reports no active probe.\n\nThe same check has appeared in [PATCH v10 2/4] of the original LoongArch\nKprobes series, but was dropped before the feature reached mainline."}],"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"},"scenarios":[{"lang":"en","value":"AV:L - An unprivileged LoongArch process reaches do_bp() then kprobe_singlestep_handler() by executing break 11 (BRK_KPROBE_SSTEPBP). That is a local CPU exception path, not a network protocol, adjacent wireless/Bluetooth frame, or physical device interface.\nAC:L - With no kprobe running on the CPU (the normal case), break 11 always takes the unmatched preempt_enable_no_resched() path and underflows preempt_count. The attacker then calls socket() from their own SIGTRAP handler; no race or victim-controlled state is required.\nPR:L - do_bp() applies no capability or credential check before dispatching BRK_KPROBE_SSTEPBP. Any unprivileged local user who can run code can issue the instruction; init-namespace root and user-namespace capabilities are not required.\nUI:N - The attacker executes break 11 in their own process and, for the cgroup bypass, installs their own SIGTRAP handler that creates sockets. No other user must mount a filesystem, open a device, or otherwise cooperate.\nS:U - Preempt-count corruption and the resulting socket cgroup/BPF misattribution stay inside the host kernel's security authority. This is not a KVM/Xen guest-to-host escape or an IOMMU/DMA boundary bypass.\nC:H - cgroup_sk_alloc() treats the underflow as interrupt context and pins the new socket to the root cgroup, so BPF_CGROUP_INET_SOCK_CREATE and later cgroup bind/connect/egress programs on the task's cgroup do not run. In a container or Cilium-style deployment this bypasses network isolation and can expose protected services.\nI:H - Root-cgroup attribution skips the container's cgroup BPF socket and traffic hooks for that socket, fully bypassing that access-control policy, while the unmatched preempt_enable corrupts kernel preempt_count used for interrupt and atomic accounting.\nA:H - The underflow makes in_atomic() true, so the next schedule (default SIGTRAP teardown or any blocking syscall) hits BUG: scheduling while atomic and can panic the host, especially with panic_on_warn. mem_cgroup_sk_alloc() also skips container socket charging, allowing host memory exhaustion."}]}],"providerMetadata":{"dateUpdated":"2026-09-16T14:39:50.410Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/ff40e597d5d98c0c45a4d09df8177202fac9520e"},{"url":"https://git.kernel.org/stable/c/a1cb727fa27c2d9c7859729cd90db7bc0f46957f"},{"url":"https://git.kernel.org/stable/c/76395109a051b53860faaec96522ef08ae9e8e27"},{"url":"https://git.kernel.org/stable/c/c4357ebeee63cb8da1446fc936573a34e68b0f71"},{"url":"https://git.kernel.org/stable/c/72ce4b24676e8b3b75376c4c559dd81c1ac52d5a"}],"title":"LoongArch: Avoid preempt count underflow without probe","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89902","datePublished":"2026-09-16T10:32:01.655Z","dateReserved":"2026-09-11T19:38:34.774Z","dateUpdated":"2026-09-16T14:39:50.410Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-16 11:16:59","lastModifiedDate":"2026-09-16 15:18:16","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"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"},"exploitabilityScore":1.8,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89902","Ordinal":"1","Title":"LoongArch: Avoid preempt count underflow without probe","CVE":"CVE-2026-89902","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89902","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nLoongArch: Avoid preempt count underflow without probe\n\nLoongArch uses break 11 for the breakpoint placed after an instruction\nthat Kprobes executes out of line. Since userspace can issue the same\nbreak instruction, do_bp() can reach kprobe_singlestep_handler() when\nthere is no current probe.\n\nThe handler actually returns false in this case, but it first calls\npreempt_enable_no_resched(). The corresponding preempt_disable() is done\nby kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run\nhere. As a result, an ordinary userspace breakpoint (code 11) underflows\nthe current task's preempt count.\n\nThis also makes in_interrupt() return true until the task schedules. One\nvisible consequence is the socket cgroup attribution: cgroup_sk_alloc()\ntreats the allocation as interrupt context and assigns the socket to the\nroot cgroup. A socket opened from the SIGTRAP handler can then avoid a\nBPF_CGROUP_INET_SOCK_CREATE policy attached to the task's own cgroup.\n\nReturn as soon as kprobe_running() reports no active probe.\n\nThe same check has appeared in [PATCH v10 2/4] of the original LoongArch\nKprobes series, but was dropped before the feature reached mainline.","Type":"Description","Title":"LoongArch: Avoid preempt count underflow without probe"}]}}}