CVE-2026-74621: net/sched: act_ct: fix sk_buff leak when the header checks reject a packet

highCVSS 7.5CVE-2026-74621

CSIRTS triage

vendor: Linux product: Linux Kernel Denial of service

What: The act_ct traffic control action leaks socket buffers when header checks reject packets, causing memory exhaustion.
Who is affected: Systems using connection tracking in traffic control with active network filtering.
Urgency: High priority; CVSS 7.5 indicates significant impact; memory leak can cause denial of service.
Action: Apply kernel patches addressing CVE-2026-74621 when available through distribution updates.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.5
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-74621

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-746210.49% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 40% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-74621	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for net/sched

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-74704: In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_cake: drop …nvd · 2026-08-22
highCVE-2026-74700: In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: Always…nvd · 2026-08-22
highCVE-2026-74663: In the Linux kernel, the following vulnerability has been resolved: net/sched: reject overly d…nvd · 2026-08-22
highCVE-2026-74621: In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: fix sk_…nvd · 2026-08-22
unknownCVE-2026-74620: In the Linux kernel, the following vulnerability has been resolved: net/sched: act_gact, act_p…nvd · 2026-08-22
highCVE-2026-74583: In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_route: fix …nvd · 2026-08-21