CVE-2026-74391 tracing: Bound synthetic-field strings with seq_buf
A buffer overflow in Linux kernel tracing allows local attackers to execute arbitrary code or escalate privileges via crafted synthetic field strings.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74391?
CVE-2026-74391 is a memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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 ]
Which versions are affected by CVE-2026-74391?
How do I fix CVE-2026-74391?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-74391 being exploited?
There is no known exploitation of CVE-2026-74391 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74391, DEBIAN-CVE-2026-74391, GHSA-853c-pg29-mfgr, UBUNTU-CVE-2026-74391.