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.
- 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-2026-64324?
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.
Which versions are affected by CVE-2026-64324?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64324?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
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
Sources
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 and 1 more.