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CVE-2026-90050· NVD / CVE Program· CNA Linux

net/sched: fq: clamp quantum and initial_quantum in change path

In the Linux kernel, the following vulnerability has been resolved: net/sched: fq: clamp quantum and initial_quantum in change path The fq change path accepts TCA_FQ_QUANTUM in [1, INT_MAX] and TCA_FQ_INITIAL_QUANTUM up to INT_MAX, while fq_init() already clamps to [1, 1<<20]. A user can override the init clamp via tc qdisc change, restoring the small-quantum deficit spin that the init clamp prevents. Narrow iq_range.max to 1<<20 so TCA_FQ_INITIAL_QUANTUM is rejected at parse time. Clamp TCA_FQ_QUANTUM to [256, 1<<20] in fq_change() and fq_init() quantum to [256, 1<<20] for tiny-MTU devices. Conditions to recreate the bug: CONFIG_NET_SCH_FQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root fq tc qdisc change dev dummy0 root fq quantum 1 stab data 32768 size_log 15 cell_log 0

—No exploit Fix available
Published
Sep 17, 2026
Updated
Sep 17, 2026
EPSS
0.2% · 10th percentile
CWE
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Action score

0

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Low priority for now.

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

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Affected systems

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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

    • 7.3-rc1affected
    • d16dac3925be95ad46e986d4b139c9898b6e227f and later · before a27498d34c3f429fb6db3aa609569f8154afa175affected · git
    • f6b3e3848a5fca63438984acd6d9eceac80814c1 and later · before 798283cd0fe7ba997f67e5a917f14ab40afa8d9faffected · git
    • e35acd56f244d94355f9ab237c2ecc8fba5e6f04 and later · before 72e9387884554f47b03bfd40fb8b2bf52789c68daffected · git
    • 709f34f7c28dc4dd6c40343d101850f11e172312 and later · before 094cc07f98dfe70a34e2a1923af17fd29b8cf622affected · git
    • before 7.3-rc1not affected · semver
    • 7.3-rc3 and laternot affected · original_commit_for_fix

Same product

linux: all records

Other highest-scoring records for the same primary product.

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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 Linux094cc07f98dfe70a34e2a1923af17fd29b8cf622Vendor (CNA)
Linux Linux72e9387884554f47b03bfd40fb8b2bf52789c68dVendor (CNA)
Linux Linux798283cd0fe7ba997f67e5a917f14ab40afa8d9fVendor (CNA)
Linux Linuxa27498d34c3f429fb6db3aa609569f8154afa175Vendor (CNA)

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

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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.

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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)

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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

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

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