# CVE-2026-97554: smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr()

> A Linux kernel SMB client flaw allows leaking kernel stack contents to userspace when processing malformed directory entries from an untrusted server.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-104337, BELL-CVE-2026-97554, DEBIAN-CVE-2026-97554, GHSA-vfwc-r92w-jp29, UBUNTU-CVE-2026-97554

## What is CVE-2026-97554?

CVE-2026-97554 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2026-97554?


## How do I fix CVE-2026-97554?

Apply the vendor's patch.

## Is CVE-2026-97554 being exploited?

There is no known exploitation of CVE-2026-97554 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97554 and fix it if it is affected.

What it is: CVE-2026-97554 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-97554 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-97554/ (Markdown: https://insights.sbomify.com/CVE-2026-97554/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97554
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97554
- OSV: https://osv.dev/vulnerability/CVE-2026-97554

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97554/
Summaries are generated and may contain mistakes; the official description above is the record.