PT-2026-64700 · Linux · Linux
CVE-2026-64479
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Published
2026-07-25
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Updated
2026-07-25
None
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In the Linux kernel, the following vulnerability has been resolved:
ALSA: seq: Fix uninitialised heap leak in snd seq event dup()
snd seq event dup() copies an incoming event into a pool cell and, in
the UMP-enabled build, clears the trailing cell->ump.raw.extra word that
the memcpy() did not cover. The guard deciding whether to clear it
compares the copied size against sizeof(cell->event):
memcpy(&cell->ump, event, size);
if (size < sizeof(cell->event))
cell->ump.raw.extra = 0;For a legacy (non-UMP) event, size == sizeof(struct snd seq event) ==
sizeof(cell->event), so the condition is false and the extra word keeps
stale data. The cell pool is allocated with kvmalloc() (not zeroed) and
cells are reused via a free list, so that word holds uninitialised heap
or leftover event data.
When such a cell is delivered to a UMP client (client->midi version > 0)
that set SNDRV SEQ FILTER NO CONVERT -- so the legacy event reaches it
unconverted -- snd seq read() reads it out as the larger struct
snd seq ump event and copies the stale word to user space, a 4-byte
kernel heap infoleak to an unprivileged /dev/snd/seq client.
Compare against sizeof(cell->ump) instead, so the trailing word is zeroed
for every event shorter than the UMP cell.
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Related Identifiers
Affected Products
Linux