net/sched: fq: add overflow bounds to quantum and initial quantum
Summary
| CVE | CVE-2026-90076 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-17 17:16:56 UTC |
| Updated | 2026-10-30 13:20:40 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: net/sched: fq: add overflow bounds to quantum and initial quantum fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 * psched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit arithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill loop adds 0 to f->credit (which stays <= 0) and goto begin loops forever under the qdisc lock, creating a soft lockup. Clamp psched_mtu() to [1, 1 << 20] before multiplying so the product cannot wrap, then cap the result at 1 << 20, matching the bound already enforced on TCA_FQ_QUANTUM in fq_change(). Conditions to recreate the bug: a device whose MTU (plus hard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace. |
Risk And Classification
EPSS: 0.002060000 probability, percentile 0.107100000 (date 2026-10-30)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected afe4fd062416b158a8a8538b23adc1930a9b88dc cf398f67d9caa71af3b9fb9319058b22fe6b524e git | Not specified |
| CNA | Linux | Linux | affected afe4fd062416b158a8a8538b23adc1930a9b88dc fd63409b669f9951f1cc6b02486a5254103800d1 git | Not specified |
| CNA | Linux | Linux | affected afe4fd062416b158a8a8538b23adc1930a9b88dc d16dac3925be95ad46e986d4b139c9898b6e227f git | Not specified |
| CNA | Linux | Linux | affected afe4fd062416b158a8a8538b23adc1930a9b88dc f6b3e3848a5fca63438984acd6d9eceac80814c1 git | Not specified |
| CNA | Linux | Linux | affected afe4fd062416b158a8a8538b23adc1930a9b88dc e35acd56f244d94355f9ab237c2ecc8fba5e6f04 git | Not specified |
| CNA | Linux | Linux | affected afe4fd062416b158a8a8538b23adc1930a9b88dc 709f34f7c28dc4dd6c40343d101850f11e172312 git | Not specified |
| CNA | Linux | Linux | affected 3.12 | Not specified |
| CNA | Linux | Linux | unaffected 3.12 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.1.191 6.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.160 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.110 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.52 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2.6 7.2.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.3 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/cf398f67d9caa71af3b9fb9319058b22fe6b524e | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/fd63409b669f9951f1cc6b02486a5254103800d1 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.