Linux Kernel io_uring SQPOLL Use-After-Free in task_work
CVE-2026-98858 Published on October 18, 2026
io_uring: fix task_work add use-after-free with SQPOLL
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.
Products Associated with CVE-2026-98858
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Affected Versions
Linux:- Version af5d68f8892f8ee8f137648b79ceb2abc153a19b and below 42b3332efacfd2140be4cd0dedad4fb96b8ae90e is affected.
- Version af5d68f8892f8ee8f137648b79ceb2abc153a19b and below 891bd8335a0de3bb15c3b797ce3026bbb0dbef6c is affected.
- Version af5d68f8892f8ee8f137648b79ceb2abc153a19b and below 395b25968fe854d4efaa19a8e9b7a5b6d1b3eea3 is affected.
- Version af5d68f8892f8ee8f137648b79ceb2abc153a19b and below a92193c91e8839fe5fc209616ea95465ae4b919d is affected.
- Version 6.9 is affected.
- Before 6.9 is unaffected.
- Version 6.12.113, <= 6.12.* is unaffected.
- Version 6.18.56, <= 6.18.* is unaffected.
- Version 7.2.10, <= 7.2.* is unaffected.
- Version 7.3-rc6, <= * is unaffected.