Bug 2562731 (CVE-2026-99181)

Summary: CVE-2026-99181 kernel: kernel: Denial of Service via improper notification pipe error handling in autofs
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's autofs (automount file system) subsystem. A local attacker can cause a Denial of Service (DoS) by initiating file system lookups while the automount daemon is restarting. Due to mishandled errors from an obsolete communication pipe, the kernel incorrectly shuts down the newly replaced pipe, causing subsequent autofs lookups and mount requests to fail.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-10-28 10:58:52 UTC 
In the Linux kernel, the following vulnerability has been resolved:

autofs: ignore notification errors from a replaced pipe

autofs_notify_daemon() takes a reference to the current notification
pipe under wq_mutex, then drops the mutex before writing the request. The
write can block while the daemon enters catatonic mode and installs a
replacement pipe.

If the old pipe's reader is then closed, the delayed write returns -EPIPE
and the generic error path enters catatonic mode again. That transition
acts on the current superblock state, closes the replacement pipe, and
releases the new daemon generation's wait queues.

Only enter catatonic mode when the pipe which failed is still the current
pipe. Factor the already-locked transition so the identity check and state
change are atomic with respect to another replacement.

This was reproduced on v7.3-rc5-337-gff47652a4b66c in a local QEMU guest.
An unprivileged UID 65534 lookup filled the old packet pipe before a
normal CATATONIC/SETPIPEFD restart. On the unmodified kernel, the new pipe
received HUP and both a pending victim lookup and a later lookup failed
with ENOENT in two out of two fresh-mount runs.

With this change, the new pipe remained active, received an intact
304-byte request, and both victim lookups completed in two out of two
runs. Normal lookup and restart-without-a-blocked-writer controls passed.
No KASAN, oops, refcount, or lock diagnostic was observed. A source
reproducer and complete local logs are available privately on request.

The demonstrated impact is limited to denial of a shared autofs service
during a legitimate daemon restart. No memory corruption, information leak,
privilege escalation, or code execution primitive was observed.