CVE-2026-90220

Published Sep 17, 2026

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.

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References

Frequently Asked Questions

What is CVE-2026-90220? +
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.
How do I check if I'm vulnerable to CVE-2026-90220? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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