# CVE-2025-40049: Squashfs: fix uninit-value in squashfs_get_parent

> A local attacker can trigger an uninitialized value access in the Squashfs filesystem, potentially leaking kernel memory information.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Oct 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-68915, BELL-CVE-2025-40049, DEBIAN-CVE-2025-40049, GHSA-pq9p-38r9-fjq5, ROOT-OS-DEBIAN-11-CVE-2025-40049, ROOT-OS-UBUNTU-2204-CVE-2025-40049, ROOT-OS-UBUNTU-2404-CVE-2025-40049, UBUNTU-CVE-2025-40049

## What is CVE-2025-40049?

CVE-2025-40049 is a vulnerability in Linux, published on 28 Oct 2025. 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:

Squashfs: fix uninit-value in squashfs_get_parent

Syzkaller reports a "KMSAN: uninit-value in squashfs_get_parent" bug.

This is caused by open_by_handle_at() being called with a file handle
containing an invalid parent inode number.  In particular the inode number
is that of a symbolic link, rather than a directory.

Squashfs_get_parent() gets called with that symbolic link inode, and
accesses the parent member field.

	unsigned int parent_ino = squashfs_i(inode)->parent;

Because non-directory inodes in Squashfs do not have a parent value, this
is uninitialised, and this causes an uninitialised value access.

The fix is to initialise parent with the invalid inode 0, which will cause
an EINVAL error to be returned.

Regular inodes used to share the parent field with the block_list_start
field.  This is removed in this commit to enable the parent field to
contain the invalid inode number 0.

## Which versions are affected by CVE-2025-40049?


## How do I fix CVE-2025-40049?

Apply the vendor's patch.

## Is CVE-2025-40049 being exploited?

There is no known exploitation of CVE-2025-40049 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40049 and fix it if it is affected.

What it is: CVE-2025-40049 is a vulnerability in Linux, published on 28 Oct 2025. 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-2025-40049 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-2025-40049/ (Markdown: https://insights.sbomify.com/CVE-2025-40049/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40049
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40049
- OSV: https://osv.dev/vulnerability/CVE-2025-40049

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40049/
Summaries are generated and may contain mistakes; the official description above is the record.