CVE-2026-90220 ALSA: seq: Don't leak the extension cell pointer in the bounce payload
An unprivileged local attacker can leak kernel memory addresses via ALSA sequencer bounce events, aiding further exploitation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90220?
CVE-2026-90220 is a vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ALSA: seq: Don't leak the extension cell pointer in the bounce payload
The bounce_error_event() embeds the failed event in the bounce payload by pointing data.ext.ptr at it. When that event is a queued variable-length event, its own data.ext.ptr holds the address of its first extension cell, put there by snd_seq_event_dup(). The payload goes out verbatim through snd_seq_expand_var_event(), so the address reaches userspace.
That is the same address commit 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read") removed from the event header. The read path still clears it there, just above the call that expands the payload.
Embed a sanitised copy instead, treated exactly as snd_seq_read() treats the header. A stack copy is enough because delivery is synchronous and snd_seq_event_dup() copies before returning.
An unprivileged client reaches this by setting SNDRV_SEQ_FILTER_BOUNCE, queueing a variable-length event to a port that does not exist and reading the bounce back. Eight bytes on 64-bit, from its own pool.
Which versions are affected by CVE-2026-90220?
How do I fix CVE-2026-90220?
Apply the vendor's patch.
Is CVE-2026-90220 being exploited?
There is no known exploitation of CVE-2026-90220 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-90220, DEBIAN-CVE-2026-90220, GHSA-r7hx-2638-9jpm, UBUNTU-CVE-2026-90220.