CVE Catalog

CVE-2026-64479

Low risk· EPSS 8%
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.18%

8th percentile - higher than 8% of all known CVEs

Summary

In the Linux kernel's ALSA seq, snd_seq_event_dup() leaks uninitialized heap data. For legacy (non-UMP) events, the trailing word in cell->ump.raw.extra is not zeroed, causing uninitialized heap data or leftover event data to be copied to user space.

Risk Assessment

An unprivileged /dev/snd/seq client can read 4 bytes of uninitialized kernel heap memory, resulting in an information leak (infoleak).

Recommendation

Apply the Linux kernel patch that compares the copy size against sizeof(cell->ump) instead of sizeof(cell->event) to ensure the extra word is zeroed.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS