Executive brief
A vulnerability in the Linux kernel's AppArmor security module could allow a local administrator to cause a system crash. AppArmor, which restricts the capabilities of programs to enhance security, fails to properly handle certain data tables that are not correctly aligned in memory. This can lead to unaligned memory access errors on specific hardware architectures, resulting in a kernel panic or system instability.
Technical details
A vulnerability exists in the AppArmor component of the Linux kernel, specifically within the 'aa_dfa_unpack' function in 'security/apparmor/match.c'. The issue arises because Deterministic Finite Automaton (DFA) tables, which can be provided by userspace via 'apparmor_parser', are not guaranteed to be 8-byte aligned. On architectures that do not support unaligned memory access (such as SPARC), this triggers a kernel warning or oops when the kernel attempts to cast and dereference these pointers as '__be32' or '__be16' types. An attacker with sufficient privileges to load or replace AppArmor profiles could exploit this to cause a Denial of Service (DoS). The fix involves using 'get_unaligned_be32()' and 'get_unaligned_be16()' helpers to safely access memory regardless of alignment.
Affected products
- Linux Linux kernel 6.18.0-rc6+; fixed in 6.1.x, 6.6.x, 6.12.x, 6.13.x
Timeline
- 2025-11-25: other: Patch authored by Helge Deller
- 2026-06-03: advisory: CVE-2026-46254 published by NVD