CVE-2026-53175

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush

On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and

flushes every fragment queue that is not yet complete using

inet_frag_queue_flush(). That helper frees all the skbs queued on the

fragment queue but does not set INET_FRAG_COMPLETE, and leaves

q->fragments_tail and q->last_run_head pointing at the freed skbs.

The queue itself stays in the rhashtable.

fqdir_pre_exit() first lowers high_thresh to 0 to stop new queue lookups,

but it cannot stop a fragment that already obtained the queue through

inet_frag_find() earlier and stalled just before taking the queue lock.

Once that fragment resumes after the flush and takes the queue lock,

it passes the INET_FRAG_COMPLETE check and then dereferences the freed

fragments_tail. inet_frag_queue_insert() reads FRAG_CB() and ->len of

that pointer and, on the append path, writes ->next_frag, causing

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References