# CVE-2026-45991: udf: fix partition descriptor append bookkeeping

> A heap out-of-bounds write in the Linux kernel UDF filesystem allows attackers to execute arbitrary code or escalate privileges via a crafted image.

- **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:** 27 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-88721, BELL-CVE-2026-45991, DEBIAN-CVE-2026-45991, GHSA-x889-prf3-g3vg, ROOT-OS-DEBIAN-11-CVE-2026-45991, ROOT-OS-DEBIAN-12-CVE-2026-45991, ROOT-OS-UBUNTU-2204-CVE-2026-45991, ROOT-OS-UBUNTU-2404-CVE-2026-45991, UBUNTU-CVE-2026-45991

## What is CVE-2026-45991?

CVE-2026-45991 is a high-severity memory corruption vulnerability in Linux kernel, published on 27 May 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: fix partition descriptor append bookkeeping

Mounting a crafted UDF image with repeated partition descriptors can
trigger a heap out-of-bounds write in part_descs_loc[].

handle_partition_descriptor() deduplicates entries by partition number,
but appended slots never record partnum. As a result duplicate
Partition Descriptors are appended repeatedly and num_part_descs keeps
growing.

Once the table is full, the growth path still sizes the allocation from
partnum even though inserts are indexed by num_part_descs. If partnum is
already aligned to PART_DESC_ALLOC_STEP, ALIGN(partnum, step) can keep
the old capacity and the next append writes past the end of the table.

Store partnum in the appended slot and size growth from the next append
count so deduplication and capacity tracking follow the same model.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-45991?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-45991?

Apply the vendor's patch.

## Is CVE-2026-45991 being exploited?

There is no known exploitation of CVE-2026-45991 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-2026-45991 and fix it if it is affected.

What it is: CVE-2026-45991 is a high-severity memory corruption vulnerability in Linux kernel, published on 27 May 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-2026-45991 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-2026-45991/ (Markdown: https://insights.sbomify.com/CVE-2026-45991/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45991
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45991
- OSV: https://osv.dev/vulnerability/CVE-2026-45991

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45991/
Summaries are generated and may contain mistakes; the official description above is the record.