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CVE-2026-98116

Linux: ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
7.8High
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.13%Chance of exploitation activity in the next 30 days, higher than 2% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in9857a75714bb5df4781e4d8b1a1753b1e17bf07aAlso 8c1882dfee8f404d118020664b73eb4592172226, 9b110a9dcecc59516c77cb3c0caf1f492f75df2d and 7 moreCVE List
Published25 Sep 2026Updated 19 Oct 2026CVE List

What fixes it

Show all 10 fixed versions

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

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.

Text from CVE List

Affected versions 29

  • Linuxaffected: 33061d0fba51d2bf70a2ef9645f703c33fe8e438 before e6cdd2a0470d64073349a970dc1691433804b271CVE List
  • Linuxaffected: 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before 9857a75714bb5df4781e4d8b1a1753b1e17bf07aCVE List
  • Linuxaffected: 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before cbadf2575d25e7dcc0d4da2717817ae569fbc99bCVE List
  • Linuxaffected: 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5CVE List
  • Linuxaffected: 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before fd137bf8149bc6460f9b7b1fc292025da04cb9eeCVE List
  • Linuxaffected: 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before 8c1882dfee8f404d118020664b73eb4592172226CVE List
  • Linuxaffected: 92ee3c60ec9fe64404dc035e7c41277d74aa26cb before 9b110a9dcecc59516c77cb3c0caf1f492f75df2dCVE List
  • Linuxaffected: a42aa926843acca96c0dfbde2e835b8137f2f092CVE List
  • Linuxaffected: 9cb6c40a6ebe4a0cfc9d6a181958211682cffea9CVE List
  • Linuxaffected: fbeb492694ce0441053de57699e1e2b7bc148a69CVE List
  • Linuxaffected: 0f6947f5f5208f6ebd4d76a82a4757e2839a23f8CVE List
  • Linuxaffected: 0090c13cbbdffd7da079ac56f80373a9a1be0bf8CVE List
  • Linuxaffected: 1bbf82d9f961414d6c76a08f7f843ea068e0ab7bCVE List
  • Linuxaffected: 5.15.32 before 5.15.222CVE List
  • Linuxaffected: 4.14.279 before 4.15CVE List
  • Linuxaffected: 4.19.243 before 4.20CVE List
  • Linuxaffected: 5.4.193 before 5.5CVE List
  • Linuxaffected: 5.10.109 before 5.11CVE List
  • Linuxaffected: 5.16.18 before 5.17CVE List
  • Linuxaffected: 5.17.1 before 5.18CVE List
  • Linuxaffected: 5.18CVE List
  • Linuxunaffected: all versions before 5.18CVE List
  • Linuxunaffected: 5.15.222 through 5.15.*CVE List
  • Linuxunaffected: 6.1.189 through 6.1.*CVE List
  • Linuxunaffected: 6.6.158 through 6.6.*CVE List
  • Linuxunaffected: 6.12.111 through 6.12.*CVE List
  • Linuxunaffected: 6.18.53 through 6.18.*CVE List
  • Linuxunaffected: 7.2.7 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 7