CVE-2026-98130

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.

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/00b841bac10230c557be6b38efc48508198fe23e
• https://git.kernel.org/stable/c/09e7f9290d63178f56095d5c18fb9f9470153db5
• https://git.kernel.org/stable/c/2188569e7e1b0bc3f3b557dc97ab7a02befc11c8
• https://git.kernel.org/stable/c/3205a20f837f5b1f009427ac3d9f706bf8a6fbec
• https://git.kernel.org/stable/c/3d698d1e6c8bc41e3e1707777a016f1bdd07842d
• https://git.kernel.org/stable/c/755d70ca845fd9b87c7b338ae6ae832b08cd0005
• https://git.kernel.org/stable/c/cbf2df9aac4202f9fb0b361a7fe8c79b29fad92c
• https://git.kernel.org/stable/c/e42ba56281ca3ae2dcb3558bebee9a1c9a4831d9