CVE-2026-98116
Analyzed
Analyzed - Analysis Complete
Use-After-Free in Linux Kernel ALSA PCM Subsystem
Vulnerability report for CVE-2026-98116, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-25
Last updated on: 2026-10-28
Assigner: kernel.org
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | From 6.19 (inc) to 7.2.7 (exc) |
| linux | linux_kernel | 7.3 |
| linux | linux_kernel | From 6.13 (inc) to 6.18.53 (exc) |
| linux | linux_kernel | From 4.14.279 (inc) to 4.15 (exc) |
| linux | linux_kernel | From 4.19.243 (inc) to 4.20 (exc) |
| linux | linux_kernel | From 5.10.109 (inc) to 5.11 (exc) |
| linux | linux_kernel | From 5.4.193 (inc) to 5.5 (exc) |
| linux | linux_kernel | From 6.7 (inc) to 6.12.111 (exc) |
| linux | linux_kernel | From 5.15.32 (inc) to 5.15.222 (exc) |
| linux | linux_kernel | From 5.16.18 (inc) to 5.17.1 (inc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-416 | The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. |
