VulnerabilityPublished 17 Sep 2026Updated 21 Oct 2026

CVE-2026-90076: Linux kernel · net/sched: fq: add overflow bounds to quantum and initial quantum

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in fd63409b669f9951f1cc6b02486a5254103800d1 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in fd63409b669f9951f1cc6b02486a5254103800d1, f6b3e3848a5fca63438984acd6d9eceac80814c1, e35acd56f244d94355f9ab237c2ecc8fba5e6f04 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ afe4fd062416b158a8a8538b23adc1930a9b88dc, < fd63409b669f9951f1cc6b02486a5254103800d1	Fixed in fd63409b669f9951f1cc6b02486a5254103800d1
LinuxLinux	Affected ≥ afe4fd062416b158a8a8538b23adc1930a9b88dc, < f6b3e3848a5fca63438984acd6d9eceac80814c1	Fixed in f6b3e3848a5fca63438984acd6d9eceac80814c1
LinuxLinux	Affected ≥ afe4fd062416b158a8a8538b23adc1930a9b88dc, < e35acd56f244d94355f9ab237c2ecc8fba5e6f04	Fixed in e35acd56f244d94355f9ab237c2ecc8fba5e6f04
LinuxLinux	Affected ≥ afe4fd062416b158a8a8538b23adc1930a9b88dc, < d16dac3925be95ad46e986d4b139c9898b6e227f	Fixed in d16dac3925be95ad46e986d4b139c9898b6e227f
LinuxLinux	Affected ≥ afe4fd062416b158a8a8538b23adc1930a9b88dc, < 709f34f7c28dc4dd6c40343d101850f11e172312	Fixed in 709f34f7c28dc4dd6c40343d101850f11e172312
LinuxLinux	Affected =3.12	Fixed in–

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.

References

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