Linux Kernel
CVE-2025-68768
Vulnerability Assessment
| Exploit ScenarioDerived | An attacker could exploit this vulnerability to compromise the affected system. |
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Alert meAnalysisAIv1 – Mar 12, 2026
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.
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Component: timer expiry.
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Technical ContextAI · show details
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_conntrac
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DescriptionCVE.org
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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How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
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Attack Technique
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
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