{"api_version":"1","generated_at":"2026-09-20T02:46:19+00:00","cve":"CVE-2026-90076","urls":{"html":"https://cve.report/CVE-2026-90076","api":"https://cve.report/api/cve/CVE-2026-90076.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-90076","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-90076"},"summary":{"title":"net/sched: fq: add overflow bounds to quantum and initial quantum","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: fq: add overflow bounds to quantum and initial quantum\n\nfq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 *\npsched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy\nwith max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return\n0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit\narithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill\nloop adds 0 to f->credit (which stays <= 0) and goto begin loops\nforever under the qdisc lock, creating a soft lockup.\n\nClamp psched_mtu() to [1, 1 << 20] before multiplying so the product\ncannot wrap, then cap the result at 1 << 20, matching the bound already\nenforced on TCA_FQ_QUANTUM in fq_change().\n\nConditions to recreate the bug: a device whose MTU (plus\nhard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a\ndummy device with max_mtu == 0 accepting MTU 2147483634). Requires\nCAP_NET_ADMIN in a user namespace.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-17 17:16:56","updated_at":"2026-09-17 17:16:56"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04","name":"https://git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1","name":"https://git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312","name":"https://git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f","name":"https://git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-90076","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90076","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected afe4fd062416b158a8a8538b23adc1930a9b88dc d16dac3925be95ad46e986d4b139c9898b6e227f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected afe4fd062416b158a8a8538b23adc1930a9b88dc f6b3e3848a5fca63438984acd6d9eceac80814c1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected afe4fd062416b158a8a8538b23adc1930a9b88dc e35acd56f244d94355f9ab237c2ecc8fba5e6f04 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected afe4fd062416b158a8a8538b23adc1930a9b88dc 709f34f7c28dc4dd6c40343d101850f11e172312 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.12","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.12 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 6.18.52 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.6 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * 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":["net/sched/sch_fq.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"d16dac3925be95ad46e986d4b139c9898b6e227f","status":"affected","version":"afe4fd062416b158a8a8538b23adc1930a9b88dc","versionType":"git"},{"lessThan":"f6b3e3848a5fca63438984acd6d9eceac80814c1","status":"affected","version":"afe4fd062416b158a8a8538b23adc1930a9b88dc","versionType":"git"},{"lessThan":"e35acd56f244d94355f9ab237c2ecc8fba5e6f04","status":"affected","version":"afe4fd062416b158a8a8538b23adc1930a9b88dc","versionType":"git"},{"lessThan":"709f34f7c28dc4dd6c40343d101850f11e172312","status":"affected","version":"afe4fd062416b158a8a8538b23adc1930a9b88dc","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/sched/sch_fq.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"3.12"},{"lessThan":"3.12","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.110","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.52","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.6","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.110","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.52","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.6","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"3.12","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: fq: add overflow bounds to quantum and initial quantum\n\nfq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 *\npsched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy\nwith max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return\n0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit\narithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill\nloop adds 0 to f->credit (which stays <= 0) and goto begin loops\nforever under the qdisc lock, creating a soft lockup.\n\nClamp psched_mtu() to [1, 1 << 20] before multiplying so the product\ncannot wrap, then cap the result at 1 << 20, matching the bound already\nenforced on TCA_FQ_QUANTUM in fq_change().\n\nConditions to recreate the bug: a device whose MTU (plus\nhard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a\ndummy device with max_mtu == 0 accepting MTU 2147483634). Requires\nCAP_NET_ADMIN in a user namespace."}],"providerMetadata":{"dateUpdated":"2026-09-17T16:05:55.517Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f"},{"url":"https://git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1"},{"url":"https://git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04"},{"url":"https://git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312"}],"title":"net/sched: fq: add overflow bounds to quantum and initial quantum","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-90076","datePublished":"2026-09-17T16:05:55.517Z","dateReserved":"2026-09-11T19:38:34.785Z","dateUpdated":"2026-09-17T16:05:55.517Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-17 17:16:56","lastModifiedDate":"2026-09-17 17:16:56","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"90076","Ordinal":"1","Title":"net/sched: fq: add overflow bounds to quantum and initial quantu","CVE":"CVE-2026-90076","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"90076","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: fq: add overflow bounds to quantum and initial quantum\n\nfq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 *\npsched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy\nwith max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return\n0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit\narithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill\nloop adds 0 to f->credit (which stays <= 0) and goto begin loops\nforever under the qdisc lock, creating a soft lockup.\n\nClamp psched_mtu() to [1, 1 << 20] before multiplying so the product\ncannot wrap, then cap the result at 1 << 20, matching the bound already\nenforced on TCA_FQ_QUANTUM in fq_change().\n\nConditions to recreate the bug: a device whose MTU (plus\nhard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a\ndummy device with max_mtu == 0 accepting MTU 2147483634). Requires\nCAP_NET_ADMIN in a user namespace.","Type":"Description","Title":"net/sched: fq: add overflow bounds to quantum and initial quantu"}]}}}