CVE-2025-68768
Deferred Deferred - Pending Action
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-06-09

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: inet: frags: flush pending skbs in fqdir_pre_exit() We have been seeing occasional deadlocks on pernet_ops_rwsem since September in NIPA. The stuck task was usually modprobe (often loading a driver like ipvlan), trying to take the lock as a Writer. lockdep does not track readers for rwsems so the read wasn't obvious from the reports. On closer inspection the Reader holding the lock was conntrack looping forever in nf_conntrack_cleanup_net_list(). Based on past experience with occasional NIPA crashes I looked thru the tests which run before the crash and noticed that the crash follows ip_defrag.sh. An immediate red flag. Scouring thru (de)fragmentation queues reveals skbs sitting around, holding conntrack references. The problem is that since conntrack depends on nf_defrag_ipv6, nf_defrag_ipv6 will load first. Since nf_defrag_ipv6 loads first its netns exit hooks run _after_ conntrack's netns exit hook. Flush all fragment queue SKBs during fqdir_pre_exit() to release conntrack references before conntrack cleanup runs. Also flush the queues in timer expiry handlers when they discover fqdir->dead is set, in case packet sneaks in while we're running the pre_exit flush. The commit under Fixes is not exactly the culprit, but I think previously the timer firing would eventually unblock the spinning conntrack.
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Meta Information
Published
2026-01-13
Last Modified
2026-06-09
Generated
2026-06-16
AI Q&A
2026-01-14
EPSS Evaluated
2026-06-15
NVD
CVE-2025-68768
EUVD
EUVD-2026-2330
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability involves a deadlock in the Linux kernel related to the handling of fragmented network packets. Specifically, the issue occurs because fragment queues (skbs) are not properly flushed during the network namespace exit process, causing references held by the connection tracking system (conntrack) to persist. This leads to a deadlock when conntrack tries to clean up, as it loops indefinitely waiting for these references to be released. The root cause is the order in which netns exit hooks run, with nf_defrag_ipv6 running after conntrack, preventing proper cleanup. The fix involves flushing all fragment queue skbs during the fqdir_pre_exit() function to release conntrack references before cleanup.

Impact Analysis

This vulnerability can cause deadlocks in the Linux kernel networking stack, leading to system instability or crashes. Specifically, tasks such as modprobe may hang indefinitely while waiting for locks, potentially causing network services or drivers to become unresponsive. This can disrupt normal network operations and affect system reliability.

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