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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-53175

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

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Status
Published
Published
Updated
Assigning organization
Linux

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 a slab use-after-free. IPv6, nf_conntrack_reasm6 and 6lowpan reassembly share the same flush path and are affected as well. Reset rb_fragments, fragments_tail and last_run_head in inet_frag_queue_flush() so a flushed queue no longer points at the freed skbs. A fragment that resumes after the flush and takes the queue lock then finds an empty queue and starts a new run instead of dereferencing the freed fragments_tail. ip_frag_reinit() already performed this reset after its own flush, so drop the now duplicate code there.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 22ee4010866da81aeee08e1ea3fddbe418feb212 to < 0e823ca0e7391630784ae7dd0981b7ad170a93d9affected
  • 543555954b1ee8d1903a7020324efb41b0c97428 to < c22599cc90e1cd5f8129c8670bd68a02ff7177b4affected
  • c70df25214ac9b32b53e18e6ae3b8f073ffa6903 to < 89b909e9704587bfecc1aab1d37e98faee03b9f9affected
  • 006a5035b495dec008805df249f92c22c89c3d2e to < 010c3313a4d178dc2d3ce958d2e5cb055e2864c1affected
  • 006a5035b495dec008805df249f92c22c89c3d2e to < 32594b09854970d7ba83eb2dc8c69a2edd158c8eaffected
  • 6.12.93 to < 6.12.94affected
  • 6.18.3 to < 6.18.36affected

Linux Linux

Default version status: affected

  • 6.19affected
  • 0 to < 6.19unaffected
  • 6.12.94 to ≤ 6.12.*unaffected
  • 6.18.36 to ≤ 6.18.*unaffected
  • 7.0.13 to ≤ 7.0.*unaffected
  • 7.1 to ≤ *unaffected

References