Unknown

CVE-2026-90075 — net/sched: fq_codel: clamp default quantum and mtu

In the Linux kernel, the following vulnerability has been resolved: net/sched: fq_codel: clamp default quantum and mtu fq_codel_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) without clamping. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000, which overflows the signed flow->deficit to INT_MIN in fq_codel_dequeue(), causing an infinite loop and soft lockup. Emulate fq_codel_change() and constrain to [256, FQ_CODEL_QUANTUM_MAX]. The same unclamped psched_mtu() is assigned to q->cparams.mtu a bit below, and fq_codel_change() never updates it. codel_should_drop() tests "*backlog <= params->mtu"; with mtu == 0x80000000 (~2 GiB) and the default 32 MiB memory_limit, the test is always true, so CoDel is silently and completely disabled (no drops, no ECN). Declare a single clamped mtu and assign both q->quantum and q->cparams.mtu from it, which also removes the double psched_mtu() call. Conditions to recreate the bug: a device whose MTU (plus hard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace.

Published Sep 17, 2026 · Updated Oct 19, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+2

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.21%

ahead of 11% of scored CVEs · Oct 19, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < d315ee8a07fd1810880227319cf60e6cd925ef22≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < a9a5b2943a00df2ab81a2209f31dd9e87016f120≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < 3782067ec0d485628b6f1f9ede3eeeb4f611fcf2≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < 397e2b1f71d9f15b8b4e47d24eb620e4dff8878d≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < 324f86806673ae4a55f66d28db84577f46f615e1≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < dfb4b61db886917244284b18b44b23d2254b82c2≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < 9f499e5827fdb6d7fdb46a7ce731852f6b1a1bb9≥ 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and < d9ebd8f9aa8b2773235889cb903fafd61f2d8585 and 1 more version 3.5	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 15, 2026 → Oct 19, 2026 · 4 reading(s) · max 0.21%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 15, 2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 17, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 19, 2026 – Oct 19, 2026
1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

10 on the record

git.kernel.org/stable/c/3782067ec0d485628b6f1f9ede3eeeb4f611fcf2
NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-90075
GitHub Security Advisories
git.kernel.org/stable/c/397e2b1f71d9f15b8b4e47d24eb620e4dff8878d
NIST National Vulnerability Database
github.com/advisories/GHSA-cgq5-rq9f-qphv
GitHub Security Advisories
git.kernel.org/stable/c/d315ee8a07fd1810880227319cf60e6cd925ef22
NIST National Vulnerability Database
git.kernel.org/stable/c/9f499e5827fdb6d7fdb46a7ce731852f6b1a1bb9
NIST National Vulnerability Database
git.kernel.org/stable/c/d9ebd8f9aa8b2773235889cb903fafd61f2d8585
NIST National Vulnerability Database
git.kernel.org/stable/c/dfb4b61db886917244284b18b44b23d2254b82c2
NIST National Vulnerability Database
git.kernel.org/stable/c/324f86806673ae4a55f66d28db84577f46f615e1
NIST National Vulnerability Database
git.kernel.org/stable/c/a9a5b2943a00df2ab81a2209f31dd9e87016f120
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Unknown CVE-2026-98866 sched/cache: Introduce task_struct->sched_cache_grp to fix UAF 2d
Unknown CVE-2026-98867 dm-pcache: bound the logical key offset from persistent memory 2d
Unknown CVE-2026-98868 dm-pcache: reject a kset that overruns its segment 2d
Unknown CVE-2026-98856 kprobes: Skip disarmed probes when checking optkprobe overlap 2d
Unknown CVE-2026-98857 ipvs: bound LBLCR and LBLC cache growth 2d
Unknown CVE-2026-98858 io_uring: fix task_work add use-after-free with SQPOLL 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-90075 is "net/sched: fq_codel: clamp default quantum and mtu", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.21% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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