net/sched: fq: add overflow bounds to quantum and initial quantum
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
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- Confidentiality · integrity · availability
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- Fix status
- Partial Red Hat: 6 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 6.1.191, 6.6.160, 6.12.110, 6.18.52, 7.2.6, 7.3
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
Not affected: 1 product
- Red Hat Enterprise Linux 6
Timeline
- 2026-10-02 Threatist record created from CVE-2026-90076
- 2026-10-03 Alias added: GHSA-6j38-2pg6-m9mv
- 2026-10-13 Affected versions changed · Red Hat
- 2026-10-13 CVSS score added · Red Hat
- 2026-10-19 Fix available: Linux/[email protected] · CNA
- 2026-10-21 Fix available: Linux/[email protected], Linux/Linux@fd63409b669f9951f1cc6b02486a5254103800d1 · CNA
- 2026-10-21 1 new reference · CNA
- 2026-10-30 Fix available: Linux/[email protected], Linux/Linux@cf398f67d9caa71af3b9fb9319058b22fe6b524e · CNA
- 2026-10-30 1 new reference · CNA
- 2026-11-06 Affected versions changed · Red Hat
References
Other 6
- https://git.kernel.org/stable/c/cf398f67d9caa71af3b9fb9319058b22fe6b524e
- https://git.kernel.org/stable/c/fd63409b669f9951f1cc6b02486a5254103800d1
- https://git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f
- https://git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1
- https://git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04
- https://git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312
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Sources
- CVE-2026-90076 · CVE Program
- CVE-2026-90076 · NVD
- FIRST EPSS
- GHSA-6j38-2pg6-m9mv · GitHub Advisory Database · CC BY 4.0
- CVE-2026-90076 · Red Hat security data · CC BY 4.0
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