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CVE-2026-99254

UnknownEPSS 0.20%

Last modified

CVE-2026-99254 is a vulnerability of currently unknown severity. In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task which has used the ring to remove its tctx node, by task_work, and repeats that until the list is empty. io_tctx_exit_cb() doesn't touch the node while the task is in io_uring_cancel_generic(), which removes all the nodes at its end. So the work item queues the callback again as soon as it has completed, for nothing. That is more than a waste of time. EPSS estimates a 0.20% chance of exploitation in the next 30 days.

Description

In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task which has used the ring to remove its tctx node, by task_work, and repeats that until the list is empty. io_tctx_exit_cb() doesn't touch the node while the task is in io_uring_cancel_generic(), which removes all the nodes at its end. So the work item queues the callback again as soon as it has completed, for nothing. That is more than a waste of time. task_work_run() only returns when it finds the list empty. If the rings are released from inside the cancellation, because requests of other rings held the last references to their files, up to 64 work items keep sending callbacks to the one task which is running them. It never finds the list empty, never gets back to the cancellation, the nodes stay, and so it goes on: a task with 60 pairs of rings which poll each other ran 280000 callbacks in 5 seconds, 20 seconds after exit_group(). It ends when all the senders happen to be late at the same time. Until then the task keeps a CPU and the work items busy. An exiting task can't be killed meanwhile. execve() cancels the requests in the same way, so a live task can get stuck there as well, for minutes. If it takes more than five, the work items run into the WARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No privilege is needed for any of this. If the callback has met a task in cancellation, wait a little before it is sent again. Nobody has to wake the work item up for that: either the node is gone by then, or it is the turn of the next round.

Metrics

EPSS Probability
0.20%

9.5th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= d56d938b4bef3e1421a42023cdcd6e13c1f50831, < a22fb44e988b01b82235ea07f0bf0fc73e256596; >= d56d938b4bef3e1421a42023cdcd6e13c1f50831, < 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1; >= d56d938b4bef3e1421a42023cdcd6e13c1f50831, < 61c761fc21e00e45c33c2bb596be442d92fb8792; >= d56d938b4bef3e1421a42023cdcd6e13c1f50831, < 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9; >= d56d938b4bef3e1421a42023cdcd6e13c1f50831, < abdc57c7ebabaaf0b622178a6a85834e1e54ff80; >= d56d938b4bef3e1421a42023cdcd6e13c1f50831, < f334e79a11e084713e82402b1a7a0e321526992a; >= d56d938b4bef3e1421a42023cdcd6e13c1f50831, < 22e643e61b9b6299b42ff7d88bab48bccada8a5d
LinuxLinux5.12

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-99254?
In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task which has used the ring to remove its tctx node, by task_work, and repeats that until the list is empty. io_tctx_exit_cb() doesn't touch the node while the task is in io_uring_cancel_generic(), which removes all the nodes at its end. So the work item queues the callback again as soon as it has completed, for nothing. That is more than a waste of time. task_work_run() only returns when it finds the list empty. If the rings are released from inside the cancellation, because requests of other rings held the last references to their files, up to 64 work items keep sending callbacks to the one task which is running them. It never finds the list empty, never gets back to the cancellation, the nodes stay, and so it goes on: a task with 60 pairs of rings which poll each other ran 280000 callbacks in 5 seconds, 20 seconds after exit_group(). It ends when all the senders happen to be late at the same time. Until then the task keeps a CPU and the work items busy. An exiting task can't be killed meanwhile. execve() cancels the requests in the same way, so a live task can get stuck there as well, for minutes. If it takes more than five, the work items run into the WARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No privilege is needed for any of this. If the callback has met a task in cancellation, wait a little before it is sent again. Nobody has to wake the work item up for that: either the node is gone by then, or it is the turn of the next round.
How severe is CVE-2026-99254?
Severity scoring for CVE-2026-99254 is pending analysis. The EPSS model estimates a 0.20% probability of exploitation in the next 30 days.
How do I fix CVE-2026-99254?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST