CVE-2026-99203
Received
Received - Intake
Race Condition in Linux Kernel FASYNC Handling
Vulnerability report for CVE-2026-99203, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-28
Last updated on: 2026-10-28
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
pipe: preserve existing fasync readers on writer setup failure
F_SETFL and FIOASYNC decide whether to invoke ->fasync() before
pipe_fasync() takes pipe->mutex. Two enables of one O_RDWR FIFO can
therefore both enter the callback.
fasync_helper() allocates before checking for an existing entry. If the
first enable installs both entries, a second enable can update the
reader entry and then fail the allocation for the writer entry. The
error path removes the pre-existing reader entry, clearing FASYNC while
the writer entry remains registered. __fput() then skips ->fasync(), so a
later pipe notification can dereference the freed file or its f_owner.
An unprivileged memory-pressure reproducer triggers a KASAN
slab-use-after-free in send_sigio() through this path.
Keep the reader helper's result and undo the registration only if this
call added it. The pipe mutex serializes changes to both lists, so a
failed new registration still removes its reader, while a failed
duplicate preserves the existing registrations and FASYNC. Successful
duplicate enables continue to update fa_fd as before.
CVSS Scores
EPSS Scores
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Meta Information
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
