Bug 2516876 (CVE-2026-74391)

Summary: CVE-2026-74391 kernel: tracing: Bound synthetic-field strings with seq_buf
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the tracing subsystem of the Linux kernel. This vulnerability occurs because synthetic field helpers use unbounded string concatenation (strcat()) when building synthetic variable names and generated history commands. An attacker providing excessively long input for key lists, field names, or saved filters could cause a buffer overflow. This could lead to a denial of service (DoS) or other unpredictable system behavior.
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Description OSIDB Bzimport 2026-08-15 06:38:06 UTC 
In the Linux kernel, the following vulnerability has been resolved:

tracing: Bound synthetic-field strings with seq_buf

The synthetic field helpers build a prefixed synthetic variable name and
a generated hist command in fixed MAX_FILTER_STR_VAL buffers. The
current code appends those strings with raw strcat(), so long key lists,
field names, or saved filters can run past the end of the staging
buffers.

Build both strings with seq_buf and propagate -E2BIG if either the
synthetic variable name or the generated command exceeds
MAX_FILTER_STR_VAL. This keeps the existing tracing-side limit while
using the helper intended for bounded command construction.

[ sdr: Moved struct seq_buf *s for upside-down x-mas tree formatting ]
Comment 1 Keith Grant 2026-08-20 20:23:18 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081507-CVE-2026-74391-e5be@gregkh/T