CVE-2026-98116 ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF
A race condition in the Linux kernel ALSA PCM driver allows local attackers to exploit a use-after-free vulnerability for privilege escalation.
- 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-2026-98116?
CVE-2026-98116 is a high-severity use after free vulnerability in Linux kernel, published on 25 Sep 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:
ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF
snd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation with an mmap_count check performed under the PCM stream lock, but the lock is released long before the buffer is actually freed: snd_pcm_sync_stop(), constraint refinement and do_free_pages() all happen in between. snd_pcm_mmap_data(), on the other hand, takes no lock at all: it validates against the old buffer's state and dma_bytes, remaps its pages into the VMA, and only then increments mmap_count.
A concurrent mmap() can therefore slip in between the check and the free. remap_pfn_range() installs writable PTEs for the old buffer's pages without taking page references, and the subsequent do_free_pages() returns those pages to the page allocator while the VMA still maps them. This leaves a stale, writable mapping of freed pages: a page-level use-after-free that can be leveraged for local privilege escalation.
Make snd_pcm_mmap_data() participate in the buffer-access scheme introduced for hw_params/hw_free: acquire runtime->buffer_accessing before validating and remapping, and release it afterwards. Buffer reallocation already fails with -EBUSY while accessors are active, and the mmap side now fails with -EBUSY while a reallocation is in progress, so the validate/remap sequence and the check/free sequence can no longer interleave.
A reproducer that turns this race into a stale writable mapping of the freed DMA buffer pages is available on request.
Weakness: CWE-416
Which versions are affected by CVE-2026-98116?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-98116?
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-2026-98116 being exploited?
There is no known exploitation of CVE-2026-98116 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-104598, BELL-CVE-2026-98116, DEBIAN-CVE-2026-98116, GHSA-pwf2-cf6j-p6wx, UBUNTU-CVE-2026-98116.