CVE-2026-74740

A flaw was found in the Linux kernel's network scheduler (net/sched: act_api). A Time-of-Check to Time-of-Use (TOCTOU) race condition exists where a pointer can be cleared between two reads. This allows a concurrent operation to cause a NULL dereference, potentially leading to a system crash and Denial of Service (DoS).

A moderate-impact flaw was found in the Linux kernel's network scheduler traffic control actions API (net/sched: act_api) in the Red Hat Enterprise Linux and Red Hat In-Vehicle OS kernels. When handling a TC_ACT_GOTO_CHAIN action, tcf_action_exec() first checks the a->goto_chain pointer, and tcf_action_goto_chain_exec() then performs a second, independent read of the same pointer. A concurrent traffic control action update (for example a gact action replacement via tcf_action_set_ctrlact()) can clear a->goto_chain between the two reads, so the second read returns NULL and is dereferenced, causing a kernel panic. Exploiting this race requires local access with the privileges needed to configure traffic control actions, and the consequence is a system crash, i.e. a denial of service; confidentiality and integrity are not affected. Red Hat Enterprise Linux 7 is not affected because the vulnerable code is not present in that release. For Red Hat Enterprise Linux 6 Extended Lifecycle Support this flaw is recorded as out of support scope. The fix is deferred for the affected Red Hat Enterprise Linux and Red Hat In-Vehicle OS kernel streams; while the fix is deferred, the residual risk is limited to a denial of service caused by a local privileged attacker who is able to trigger the race.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.