Bug 2492820 (CVE-2026-53241)

Summary: CVE-2026-53241 kernel: ALSA: seq: dummy: fix UMP event stack overread
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Advanced Linux Sound Architecture (ALSA) sequencer dummy port. This vulnerability arises from a stack overread when processing Universal MIDI Packet (UMP) events, where the system attempts to copy a UMP-sized packet into a smaller, legacy-sized stack storage. This could allow a local attacker to cause a denial of service or potentially disclose sensitive information.
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Description OSIDB Bzimport 2026-06-25 10:07:29 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ALSA: seq: dummy: fix UMP event stack overread

The dummy sequencer port forwards events by copying an incoming
struct snd_seq_event into a stack temporary, rewriting source and
destination, and dispatching the temporary to subscribers. That legacy
event storage is smaller than struct snd_seq_ump_event.

When a UMP event reaches the dummy client, the copy leaves the UMP flag
set but only provides legacy-sized stack storage. The subscriber
delivery path then uses snd_seq_event_packet_size() and copies a
UMP-sized packet from that stack object, reading past the end of the
temporary.

Use the existing union __snd_seq_event storage and copy the packet size
reported for the incoming event before rewriting the common routing
fields. This preserves the full UMP packet for UMP events while keeping
legacy event handling unchanged.
Comment 1 TEJ RATHI 2026-06-26 07:05:51 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062511-CVE-2026-53241-6daa@gregkh/T