CVE-2026-74339

Summary

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 Software

VendorProductVersion RangeStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 14fe4f75fd5309d6b75f8e840ada88912b374207affected
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < f29243c211928114f8b906e0a3fee77c236f14c8affected
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < e0c3edd86414534cfd179fefe45b38c29c01ae7aaffected
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 6b52211eba213c461f68922708a99d8190c1fcd5affected
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 74ac1ce1f4afdb3b80b6742fa28fb86c8c51d31baffected
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c2ac9287e89916da684c2a548798351e63eb59eeaffected
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 705dd6dcbc0ea87351c660c1a6443f85f1001c76affected
LinuxLinux2.6.12affected
LinuxLinux0 < 2.6.12unaffected
LinuxLinux5.15.212 <= 5.15.*unaffected
LinuxLinux6.1.178 <= 6.1.*unaffected
LinuxLinux6.6.145 <= 6.6.*unaffected
LinuxLinux6.12.97 <= 6.12.*unaffected
LinuxLinux6.18.40 <= 6.18.*unaffected
LinuxLinux7.1.5 <= 7.1.*unaffected
LinuxLinux7.2 <= *unaffected

Weaknesses

References