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CVE-2026-98858

Linux: io_uring: fix task_work add use-after-free with SQPOLL

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.16%Chance of exploitation activity in the next 30 days, higher than 4% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in42b3332efacfd2140be4cd0dedad4fb96b8ae90eAlso 891bd8335a0de3bb15c3b797ce3026bbb0dbef6c, 395b25968fe854d4efaa19a8e9b7a5b6d1b3eea3CVE List
Published18 Oct 2026Updated 19 Oct 2026CVE List

What fixes it

  • 42b3332efacfd2140be4cd0dedad4fb96b8ae90eLinuxCVE List
  • 891bd8335a0de3bb15c3b797ce3026bbb0dbef6cLinuxCVE List
  • 395b25968fe854d4efaa19a8e9b7a5b6d1b3eea3LinuxCVE List

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:

io_uring: fix task_work add use-after-free with SQPOLL

For SQPOLL, the sqpoll thread runs task_work off its own list and doesn't need to be told about it, so it can pop and complete a request as soon as mpscq_push() has published it. If that was the last request holding the ring alive, io_ring_exit_work() then frees the ctx, stops the thread, and with it the tctx, while io_req_normal_work_add() is still looking at both after the push:

BUG: KASAN: slab-use-after-free in io_req_normal_work_add+0x439/0x510 Read of size 4 at addr ff11000000ca0000 by task repro/55 (...) BUG: KASAN: slab-use-after-free in queue_work_on+0x25/0x70 Write of size 8 at addr ff11000000c3bd00 by task repro/55

Hold an RCU read lock across the add, like io_req_local_work_add() already does, and have io_ring_exit_work() wait for a grace period for SQPOLL rings as well before freeing the ctx.

Text from CVE List

Affected versions 10

  • Linuxaffected: af5d68f8892f8ee8f137648b79ceb2abc153a19b before 42b3332efacfd2140be4cd0dedad4fb96b8ae90eCVE List
  • Linuxaffected: af5d68f8892f8ee8f137648b79ceb2abc153a19b before 891bd8335a0de3bb15c3b797ce3026bbb0dbef6cCVE List
  • Linuxaffected: af5d68f8892f8ee8f137648b79ceb2abc153a19b before 395b25968fe854d4efaa19a8e9b7a5b6d1b3eea3CVE List
  • Linuxaffected: af5d68f8892f8ee8f137648b79ceb2abc153a19b before a92193c91e8839fe5fc209616ea95465ae4b919dCVE List
  • Linuxaffected: 6.9CVE List
  • Linuxunaffected: all versions before 6.9CVE List
  • Linuxunaffected: 6.12.113 through 6.12.*CVE List
  • Linuxunaffected: 6.18.56 through 6.18.*CVE List
  • Linuxunaffected: 7.2.10 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 4