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CVE-2026-74391
tracing: Bound synthetic-field strings with seq_buf
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem kernel/trace. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74391 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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 ]
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
kernel/trace/trace_events_hist.c
- What this is
- TRACINGMAINTAINERS section matched on kernel/trace/ · linux-kernel@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_FUNCTION_TRACER|CONFIG_HIST_TRIGGERS|CONFIG_RETHOOK|CONFIG_RING_BUFFER|CONFIG_TRACEPOINTS|CONFIG_TRACE_CLOCK|CONFIG_TRACING' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormYnot built on arm64/arm64, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le
- trixieYnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, riscv64/riscv64
- forky, sidYnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64
- Y
- built in where it is built at all; some flavours do not build it
- Build switches
- CONFIG_FUNCTION_TRACER, CONFIG_HIST_TRIGGERS, CONFIG_RETHOOK, CONFIG_RING_BUFFER, CONFIG_TRACEPOINTS, CONFIG_TRACE_CLOCK, CONFIG_TRACING
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- no vector published, unrated
- Attack vector
- not published
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- kernel/trace
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.17 | 6.6.145 | 0c584c27f664 |
| 4.17 | 6.12.97 | 88b901fdc166 |
| 4.17 | 6.18.40 | baa333b2700a |
| 4.17 | 7.1.5 | cf334620036a |
| 4.17 | 7.2 | f07883450eb1 |
Why the CNA scored it this way
The kernel CNA published no CVSS vector and no reasoning for CVE-2026-74391, which is why it is shown as unrated rather than given an invented score. 6,405 of the 20,413 CVEs here carry reasoning; this is not one of them.