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.
- 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
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
Which versions are affected by CVE-2026-45991?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-45991?
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-2026-45991 being exploited?
There is no known exploitation of CVE-2026-45991 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
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 and 3 more.