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CVE-2026-74339: ALSA: seq: Clear variable event pointer on read

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-15 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: seq: Clear variable event pointer on read snd_seq_read() copies a queued variable-length event header to userspace before expanding the payload. Queued variable-length events use SNDRV_SEQ_EXT_CHAINED internally, and data.ext.ptr points at the first extension cell. The read side strips SNDRV_SEQ_EXT_* bits from data.ext.len before the copy, but it leaves data.ext.ptr untouched. A userspace sequencer client can therefore write a direct variable event to itself and read back the extension-cell kernel address from the returned header. Clear the temporary header pointer before copy_to_user(). The original queued event remains unchanged and is still passed to snd_seq_expand_var_event(), so payload expansion keeps using the internal chain.

Affected products

• Linux: 2.6.12 — fixed in 7.2

How to fix

Upgrade to a fixed version: Linux 7.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/14fe4f75fd5309d6b75f8e840ada88912b374207
• https://git.kernel.org/stable/c/6b52211eba213c461f68922708a99d8190c1fcd5
• https://git.kernel.org/stable/c/705dd6dcbc0ea87351c660c1a6443f85f1001c76
• https://git.kernel.org/stable/c/74ac1ce1f4afdb3b80b6742fa28fb86c8c51d31b
• https://git.kernel.org/stable/c/8a631e1aaa1ebbc9de916927fa01707244e18291
• https://git.kernel.org/stable/c/c2ac9287e89916da684c2a548798351e63eb59ee
• https://git.kernel.org/stable/c/e0c3edd86414534cfd179fefe45b38c29c01ae7a
• https://git.kernel.org/stable/c/f29243c211928114f8b906e0a3fee77c236f14c8

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