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NVD / CVE Program· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.21% (FIRST EPSS).
  • Fixed version: Linux Linux 324f86806673ae4a55f66d28db84577f46f615e1, 3782067ec0d485628b6f1f9ede3eeeb4f611fcf2, 397e2b1f71d9f15b8b4e47d24eb620e4dff8878d; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1.

Low priority for now. Upgrade to Linux Linux 324f86806673ae4a55f66d28db84577f46f615e1, 3782067ec0d485628b6f1f9ede3eeeb4f611fcf2, 397e2b1f71d9f15b8b4e47d24eb620e4dff8878d; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

—No exploit Fix available
Published
Sep 17, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 12th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 3.5affected
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before d315ee8a07fd1810880227319cf60e6cd925ef22affected · git
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before a9a5b2943a00df2ab81a2209f31dd9e87016f120affected · git
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before 3782067ec0d485628b6f1f9ede3eeeb4f611fcf2affected · git
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before 397e2b1f71d9f15b8b4e47d24eb620e4dff8878daffected · git
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before 324f86806673ae4a55f66d28db84577f46f615e1affected · git
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before dfb4b61db886917244284b18b44b23d2254b82c2affected · git
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before 9f499e5827fdb6d7fdb46a7ce731852f6b1a1bb9affected · git
    • 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe and later · before d9ebd8f9aa8b2773235889cb903fafd61f2d8585affected · git
    • before 3.5not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.190-16.1.190-1
Debian:12linux-6.12before 6.12.111-1~deb12u16.12.111-1~deb12u1
Debian:13linuxbefore 6.12.111-16.12.111-1
Debian:14linuxbefore 7.2.6-17.2.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-90073Sep 17, 2026 · net/sched: hhf: clamp quantum before hhf_change() to avoid overflow
    0Monitor
  • ← EarlierCVE-2026-90074Sep 17, 2026 · net/sched: fq_pie: clamp default quantum to avoid signed overflow
    0Monitor
  • Later →CVE-2026-90076Sep 17, 2026 · net/sched: fq: add overflow bounds to quantum and initial quantum
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux324f86806673ae4a55f66d28db84577f46f615e1Vendor (CNA)
Linux Linux3782067ec0d485628b6f1f9ede3eeeb4f611fcf2Vendor (CNA)
Linux Linux397e2b1f71d9f15b8b4e47d24eb620e4dff8878dVendor (CNA)
Linux Linux9f499e5827fdb6d7fdb46a7ce731852f6b1a1bb9Vendor (CNA)
Linux Linuxa9a5b2943a00df2ab81a2209f31dd9e87016f120Vendor (CNA)
Linux Linuxd315ee8a07fd1810880227319cf60e6cd925ef22Vendor (CNA)
Linux Linuxd9ebd8f9aa8b2773235889cb903fafd61f2d8585Vendor (CNA)
Linux Linuxdfb4b61db886917244284b18b44b23d2254b82c2Vendor (CNA)
azl3 kernel 6.6.150.1-1 on Azure Linux 3.0—Microsoft (MSRC)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.06.6.157.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.1.190-1 · Debian:12Package registry (OSV)
debian:linux6.12.111-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.111-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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