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

Not scored Published 11 Sep 2026 Updated 19 Oct 2026

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

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

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.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-89525 being exploited?

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

Sources

Also known as AZL-100397, BELL-CVE-2026-89525, DEBIAN-CVE-2026-89525, GHSA-383p-4f3r-q68w, UBUNTU-CVE-2026-89525.