CVE-2026-98130: sctp: fix a TOCTOU race in SCTP_CMD_TIMER_START

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-25 · updated 2026-10-22
Weakness: CWE-362

Description

In the Linux kernel, the following vulnerability has been resolved: sctp: fix a TOCTOU race in SCTP_CMD_TIMER_START The SCTP_CMD_TIMER_START handler checks timer_pending() before calling timer_reduce(). The timer can expire and detach between these operations, causing timer_reduce() to rearm the timer without taking the association reference required for the newly armed timer. The timer callback later unconditionally drops its association reference, which can leave the association reference count unbalanced and result in use-after-free during association teardown. Use the return value of timer_reduce() to determine whether the timer was actually armed. Take the association reference only when timer_reduce() successfully starts a new timer, closing the race between checking the timer state and rearming it. This issue was reported by Nico Yip (@_cyeaa_) working with TrendAI Zero Day Initiative.

Affected products

Linux kernel: from 4.19.126 before 4.20; from 5.4.44 before 5.5; from 5.6.16 before 5.7; from 5.7.1 before 5.10.271; from 5.11 before 5.15.222; from 5.16 before 6.1.189 — fixed in 4.20, 5.10.271, 5.15.222, 5.5, 5.7, 6.1.189

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.10.271, 5.15.222, 5.5. Check the vendor advisory for mitigations.

References

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