CVE-2025-71110 mm/slub: reset KASAN tag in defer_free() before accessing freed memory
A use-after-free bug in the Linux kernel SLUB allocator triggers KASAN reports and potential crashes when CONFIG_SLUB_TINY and ARM64 MTE are enabled.
- 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-2025-71110?
CVE-2025-71110 is a high-severity use after free vulnerability in Linux kernel, published on 14 Jan 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:
mm/slub: reset KASAN tag in defer_free() before accessing freed memory
When CONFIG_SLUB_TINY is enabled, kfree_nolock() calls kasan_slab_free() before defer_free(). On ARM64 with MTE (Memory Tagging Extension), kasan_slab_free() poisons the memory and changes the tag from the original (e.g., 0xf3) to a poison tag (0xfe).
When defer_free() then tries to write to the freed object to build the deferred free list via llist_add(), the pointer still has the old tag, causing a tag mismatch and triggering a KASAN use-after-free report:
BUG: KASAN: slab-use-after-free in defer_free+0x3c/0xbc mm/slub.c:6537 Write at addr f3f000000854f020 by task kworker/u8:6/983 Pointer tag: [f3], memory tag: [fe]
Fix this by calling kasan_reset_tag() before accessing the freed memory. This is safe because defer_free() is part of the allocator itself and is expected to manipulate freed memory for bookkeeping purposes.
Weakness: CWE-416
Which versions are affected by CVE-2025-71110?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-71110?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-71110 being exploited?
There is no known exploitation of CVE-2025-71110 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-71110, GHSA-m8f2-rw7m-jrxf, UBUNTU-CVE-2025-71110.