Linux Kernel io_wq Worker Ordering Vulnerability (CVE-2026-99243)
CVE-2026-99243 Published on November 3, 2026
io-wq: order the exit bit against worker creation task work
In the Linux kernel, the following vulnerability has been resolved:
io-wq: order the exit bit against worker creation task work
io_wq_exit_workers() cancels task work for queued worker creation with
task_work_cancel_match(). That has a plain load of task->task_works.
io_queue_worker_create() adds the new entry and tests IO_WQ_BIT_EXIT to
cancel it if the workqueue is already on its way out.
That must be ordered. task_work_add() has a full barrier via cmpxchg().
But io_wq_exit_start() sets the bit with set_bit() which doesn't have
any memory ordering.
So afaict, on weakly ordered architectures the exiting task may load
task_works before the store of the bit is visible. The other side tests
the bit before the store is visible as well. So the entry remains queued
with worker_refs and the exiting task waits on worker_done indefinitely.
If the task still has rings then io_uring_del_tctx_node() provides the
barrier via test_and_set_bit() in io_wq_set_exit_on_idle(). When it
has closed all rings though that barrier is gone.
Add the barrier after the set_bit().
Products Associated with CVE-2026-99243
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Affected Versions
Linux:- Version 4b4e5bbf9386d4ec21d91c0cb0fd60b9bba778ec and below 67da3eec264aeb67835886720243ae2dc1463315 is affected.
- Version 71a85387546e50b1a37b0fa45dadcae3bfb35cf6 and below a63c752157eacf49f628359822666b32503d194a is affected.
- Version 71a85387546e50b1a37b0fa45dadcae3bfb35cf6 and below 1432d881d99584105122760133caeff1dce7a9f7 is affected.
- Version 71a85387546e50b1a37b0fa45dadcae3bfb35cf6 and below 6cf012a4d5e461c788ecc9dbed67adc31a142644 is affected.
- Version 71a85387546e50b1a37b0fa45dadcae3bfb35cf6 and below 0d81cdd433b0a96c5275c01b8172e0b1f71dd595 is affected.
- Version 71a85387546e50b1a37b0fa45dadcae3bfb35cf6 and below 75395db7a9b40a2e826c838e648fef8ed1a2d174 is affected.
- Version 71a85387546e50b1a37b0fa45dadcae3bfb35cf6 and below 31fc780b75b278d37700373d54a99fdb4117fdd6 is affected.
- Version 5.15.11 and below 5.15.224 is affected.
- Version 5.16 is affected.
- Before 5.16 is unaffected.
- Version 5.15.224, <= 5.15.* is unaffected.
- Version 6.1.191, <= 6.1.* is unaffected.
- Version 6.6.161, <= 6.6.* is unaffected.
- Version 6.12.115, <= 6.12.* is unaffected.
- Version 6.18.60, <= 6.18.* is unaffected.
- Version 7.2.14, <= 7.2.* is unaffected.
- Version 7.3.1, <= 7.3.* is unaffected.