# CVE-2026-64324: udf: validate free block extents against the partition length

> A local attacker can crash the Linux kernel by mounting a crafted UDF filesystem and truncating a file, causing an out-of-bounds read and panic.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 25 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-93746, BELL-CVE-2026-64324, DEBIAN-CVE-2026-64324, GHSA-mpf7-xmx2-frhw, ROOT-OS-DEBIAN-12-CVE-2026-64324, ROOT-OS-UBUNTU-2204-CVE-2026-64324, UBUNTU-CVE-2026-64324

## What is CVE-2026-64324?

CVE-2026-64324 is a high-severity denial of service vulnerability in Linux kernel, published on 25 Jul 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:

udf: validate free block extents against the partition length

udf_free_blocks() checks the logical block number and count against the
partition length, but drops the extent offset from that final bound.  A
crafted extent can pass the guard while logicalBlockNum + offset + count
points past the partition, which later indexes past the space bitmap
array.

A single ftruncate(2) on a file backed by such an extent reliably
panics the kernel.  This is a local availability issue.  On desktop
systems where UDisks/polkit allows the active user to mount removable
UDF media without CAP_SYS_ADMIN, an unprivileged local user can supply
the crafted filesystem and trigger the panic by truncating a writable
file on it.  Systems that require root or CAP_SYS_ADMIN to mount the
image have a higher prerequisite.

No confidentiality or integrity impact is claimed: the reproduced
primitive is an out-of-bounds read of a bitmap pointer slot followed by
a kernel panic.

Use the already computed logicalBlockNum + offset + count value for the
partition length check.  Also make load_block_bitmap() reject an
out-of-range block group before indexing s_block_bitmap[], so corrupted
callers cannot walk past the flexible array.

Weakness: CWE-129 (Improper Validation of Array Index), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-64324?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64324?

Apply the vendor's patch.

## Is CVE-2026-64324 being exploited?

There is no known exploitation of CVE-2026-64324 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64324 and fix it if it is affected.

What it is: CVE-2026-64324 is a high-severity denial of service vulnerability in Linux kernel, published on 25 Jul 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-2026-64324 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-64324/ (Markdown: https://insights.sbomify.com/CVE-2026-64324/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64324
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64324
- OSV: https://osv.dev/vulnerability/CVE-2026-64324

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64324/
Summaries are generated and may contain mistakes; the official description above is the record.