SB20261007109 - Use-after-free in Linux kernel kernel/signal.c: __send_signal_locked() and posixtimer_send_sigqueue(); kernel/exit.c: release_task()

Description

This security bulletin contains information about 1 vulnerability.

1) Use-after-free (CVE-ID: CVE-2026-98256)

CWE-ID: CWE-416 - Use After Free

CVSSv4: 5.7 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

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

The vulnerability exists due to use-after-free in the Linux kernel signal-handling subsystem when handling signals during a non-leader thread's execve() operation. A local user can trigger a race between POSIX timer signal delivery and pending-signal flushing, followed by a tgkill() call that writes to freed timer memory, to cause a denial of service.

The described race requires a SIGEV_THREAD_ID timer targeting the original thread group leader, with its signal blocked and queued on that leader's pending-signal queue.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/621c365739828900f32a0c1cdfe5387528a62176
• https://git.kernel.org/stable/c/934bd95f1a6404dbb845951b823547abab05a649
• https://git.kernel.org/stable/c/d2710c8d938ae6a825a6463158e6e6f31eac792a