GHSA-J4JV-FP59-574F
Vulnerability from github – Published: 2026-06-25 09:31 – Updated: 2026-06-30 03:37In 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": [],
"aliases": [
"CVE-2026-53175"
],
"database_specific": {
"cwe_ids": [
"CWE-416",
"CWE-825"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-25T09:16:34Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ninet: frags: fix use-after-free caused by the fqdir_pre_exit() flush\n\nOn netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and\nflushes every fragment queue that is not yet complete using\ninet_frag_queue_flush(). That helper frees all the skbs queued on the\nfragment queue but does not set INET_FRAG_COMPLETE, and leaves\nq-\u003efragments_tail and q-\u003elast_run_head pointing at the freed skbs.\nThe queue itself stays in the rhashtable.\n\nfqdir_pre_exit() first lowers high_thresh to 0 to stop new queue lookups,\nbut it cannot stop a fragment that already obtained the queue through\ninet_frag_find() earlier and stalled just before taking the queue lock.\nOnce that fragment resumes after the flush and takes the queue lock,\nit passes the INET_FRAG_COMPLETE check and then dereferences the freed\nfragments_tail. inet_frag_queue_insert() reads FRAG_CB() and -\u003elen of\nthat pointer and, on the append path, writes -\u003enext_frag, causing a\nslab use-after-free. IPv6, nf_conntrack_reasm6 and 6lowpan reassembly\nshare the same flush path and are affected as well.\n\nReset rb_fragments, fragments_tail and last_run_head in\ninet_frag_queue_flush() so a flushed queue no longer points at the\nfreed skbs. A fragment that resumes after the flush and takes the\nqueue lock then finds an empty queue and starts a new run instead of\ndereferencing the freed fragments_tail. ip_frag_reinit() already\nperformed this reset after its own flush, so drop the now duplicate\ncode there.",
"id": "GHSA-j4jv-fp59-574f",
"modified": "2026-06-30T03:37:13Z",
"published": "2026-06-25T09:31:20Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53175"
},
{
"type": "WEB",
"url": "https://access.redhat.com/security/cve/CVE-2026-53175"
},
{
"type": "WEB",
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2492840"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/010c3313a4d178dc2d3ce958d2e5cb055e2864c1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0e823ca0e7391630784ae7dd0981b7ad170a93d9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/32594b09854970d7ba83eb2dc8c69a2edd158c8e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/89b909e9704587bfecc1aab1d37e98faee03b9f9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c22599cc90e1cd5f8129c8670bd68a02ff7177b4"
},
{
"type": "WEB",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53175.json"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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