ALSA: seq: Don't leak the extension cell pointer in the bounce payload

Summary

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.

Timeline

1. Sep 17, 2026, 4:07 PM UTCCVE published
2. Oct 21, 2026, 12:50 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 93d260ce43a81df579c98bee92b91316df9c1c57 · fixed in 42c3f856d13a91a0d4c302a0c6854813621136db; From dae23c545eb5a2be3b27a82fd0f611894fb8ab69 · fixed in b1e8d40663997aacaa198f37ce6893e07aaba77a; From efc86691e4d8083d9e380ea95042c2cf679f65fd · fixed in 6e6e471eef1d5d8cb056c7d364023fe048249204; From efc86691e4d8083d9e380ea95042c2cf679f65fd · fixed in 59e1592d3c270ff4642d5d6dc55c545306eb0693; From 6.12.97 · fixed in 6.12.110; From 6.18.40 · fixed in 6.18.52; From 6.6.160 · fixed in 6.7; From 7.1.5 · fixed in 7.2

• Linux Linux

  7.2

• KernelLinux

  fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 4