Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel - CVE-2026-74740

Vulnerability details

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to a time-of-check time-of-use race condition leading to a NULL pointer dereference in tcf_action_exec() and tcf_action_goto_chain_exec() in net/sched/act_api.c when handling TC_ACT_GOTO_CHAIN actions. A local user can trigger concurrent action updates and execution to cause a denial of service.

The issue occurs when a->goto_chain is cleared between separate RCU reads, causing a NULL chain pointer to be dereferenced through chain->filter_chain.

Affected software

How to mitigate CVE-2026-74740

External References

• https://git.kernel.org/stable/c/1ec48b6715c29b20105e3485206602cff6c51ae5
• https://git.kernel.org/stable/c/6b70886ebc428eed43a069c8944a931b5fb3f4e4
• https://git.kernel.org/stable/c/91d55fd1fdb85c8371ca8793c788ea7d5192383a
• https://git.kernel.org/stable/c/abceabc4408fca6a9dd52611f5d197dec9390d63
• https://git.kernel.org/stable/c/f60b396ee174206fe08ebf997d16cd3801b77b22

Related Security Bulletins

• Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel sched