CVE-2026-23191: ALSA: aloop: Fix racy access at PCM trigger
In the Linux kernel, the following vulnerability has been resolved:
ALSA: aloop: Fix racy access at PCM trigger
The PCM trigger callback of aloop driver tries to check the PCM state and stop the stream of the tied substream in the corresponding cable. Since both check and stop operations are performed outside the cable lock, this may result in UAF when a program attempts to trigger frequently while opening/closing the tied stream, as spotted by fuzzers.
For addressing the UAF, this patch changes two things: - It covers the most of code in loopbackcheckformat() with cable->lock spinlock, and add the proper NULL checks. This avoids already some racy accesses. - In addition, now we try to check the state of the capture PCM stream that may be stopped in this function, which was the major pain point leading to UAF.
Other sources
In the Linux kernel, the following vulnerability has been resolved:
ALSA: aloop: Fix racy access at PCM trigger
The PCM trigger callback of aloop driver tries to check the PCM state and stop the stream of the tied substream in the corresponding cable. Since both check and stop operations are performed outside the cable lock, this may result in UAF when a program attempts to trigger frequently while opening/closing the tied stream, as spotted by fuzzers.
For addressing the UAF, this patch changes two things: - It covers the most of code in loopbackcheckformat() with cable-lock spinlock, and add the proper NULL checks. This avoids already some racy accesses. - In addition, now we try to check the state of the capture PCM stream that may be stopped in this function, which was the major pain point leading to UAF.
— IBM
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-23191?
CVE-2026-23191 has been classified as a medium severity vulnerability affecting the ALSA subsystem.
How do I fix CVE-2026-23191?
To resolve CVE-2026-23191, users should upgrade to the latest version of the Linux kernel where the vulnerability has been patched.
What impact does CVE-2026-23191 have on systems?
CVE-2026-23191 can lead to race conditions in the PCM trigger function, potentially causing instability in audio streaming.
Is CVE-2026-23191 present in older Linux kernel versions?
Yes, CVE-2026-23191 is present in older versions of the Linux kernel that utilize the ALSA aloop driver.
How can I determine if my system is affected by CVE-2026-23191?
To check if your system is affected by CVE-2026-23191, verify the version of your Linux kernel against the patched versions.