CVE-2026-64324: Linux Kernel

High severity, CVSS 7.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Linux Linux Kernel: from 4.19.320, before 4.20 (fixed in 4.20); from 5.4.282, before 5.5 (fixed in 5.5); from 5.10.224, before 5.10.261 (fixed in 5.10.261); from 5.15.165, before 5.15.212 (fixed in 5.15.212); from 6.1.105, before 6.1.178 (fixed in 6.1.178); from 6.6.46, before 6.6.145 (fixed in 6.6.145); …

Published 2026-07-25. Last modified 2026-09-04.