Executive brief
A vulnerability in the Linux kernel's AppArmor security module can lead to system performance degradation or resource exhaustion. AppArmor is a security system that restricts the capabilities of programs to protect the operating system. An error in how it manages internal memory buffers can cause the system to waste resources, potentially slowing down operations or causing instability on multi-core systems.
Technical details
An integer underflow exists in the AppArmor LSM within the `aa_get_buffer()` function in `security/apparmor/lsm.c`. When the function retrieves a buffer from the per-CPU list, it unconditionally decrements `cache->hold`. If this value is already zero while the total count is non-zero, the unsigned decrement causes the value to wrap around to `UINT_MAX`. This logic error prevents `aa_put_buffer()` from returning buffers to the global list, leading to CPU starvation on multi-core systems and forcing the kernel to perform repeated `kmalloc` allocations. The fix introduces a check to ensure the decrement only occurs if `cache->hold` is greater than zero.
Affected products
- Linux Linux Kernel All versions including and prior to 6.x stable branches
Timeline
- 2026-01-19: other: Patch authored
- 2026-05-27: disclosed: CVE published
- 2026-05-27: advisory