# CVE-2026-89525: udf: reject VAT indexes equal to the entry count

> A crafted UDF image triggers a slab-out-of-bounds read in the Linux kernel, causing a kernel panic and potential information disclosure.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100397, BELL-CVE-2026-89525, DEBIAN-CVE-2026-89525, GHSA-383p-4f3r-q68w, UBUNTU-CVE-2026-89525

## What is CVE-2026-89525?

CVE-2026-89525 is a memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

udf: reject VAT indexes equal to the entry count

UDF 1.50 virtual partition mapping uses the VAT as an array of physical
block mappings. s_num_entries stores the number of entries in that array,
not the highest valid index. The valid VAT indexes are therefore below
s_num_entries.

udf_get_pblock_virt15() currently rejects only indexes greater than
s_num_entries. A crafted image can request index s_num_entries, pass the
bounds check, and make the kernel read one entry past the allocated VAT table.

Change the check to reject block >= s_num_entries, so the count is handled as
an exclusive upper bound.

A crafted UDF image reproduced this on origin/master commit
0e35b9b6ec0ffcc5e23cbdec09f5c622ad532b53 with a KASAN slab-out-of-bounds
report in udf_get_pblock_virt15().

Trail of Bits has a reproducer that triggers kernel panic demonstrating the bug, and can share it if needed.

## Which versions are affected by CVE-2026-89525?


## How do I fix CVE-2026-89525?

Apply the vendor's patch.

## Is CVE-2026-89525 being exploited?

There is no known exploitation of CVE-2026-89525 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89525 and fix it if it is affected.

What it is: CVE-2026-89525 is a memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-89525 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-2026-89525/ (Markdown: https://insights.sbomify.com/CVE-2026-89525/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89525
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89525
- OSV: https://osv.dev/vulnerability/CVE-2026-89525

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89525/
Summaries are generated and may contain mistakes; the official description above is the record.