Bug 2454821 (CVE-2026-23473)

Summary: CVE-2026-23473 kernel: io_uring/poll: fix multishot recv missing EOF on wakeup race
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel's `io_uring/poll` subsystem. A race condition can occur when a socket performs send and shutdown operations in quick succession. This can cause a multishot receive operation to hang indefinitely, leading to a Denial of Service (DoS) for affected systems.
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Description OSIDB Bzimport 2026-04-03 16:02:36 UTC 
In the Linux kernel, the following vulnerability has been resolved:

io_uring/poll: fix multishot recv missing EOF on wakeup race

When a socket send and shutdown() happen back-to-back, both fire
wake-ups before the receiver's task_work has a chance to run. The first
wake gets poll ownership (poll_refs=1), and the second bumps it to 2.
When io_poll_check_events() runs, it calls io_poll_issue() which does a
recv that reads the data and returns IOU_RETRY. The loop then drains all
accumulated refs (atomic_sub_return(2) -> 0) and exits, even though only
the first event was consumed. Since the shutdown is a persistent state
change, no further wakeups will happen, and the multishot recv can hang
forever.

Check specifically for HUP in the poll loop, and ensure that another
loop is done to check for status if more than a single poll activation
is pending. This ensures we don't lose the shutdown event.
Comment 1 Jon Moroney 2026-04-03 18:53:06 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026040323-CVE-2026-23473-ab6c@gregkh/T