{"id":"CVE-2026-53175","state":"PUBLISHED","title":"inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush","description":"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->fragments_tail and q->last_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 ->len of\nthat pointer and, on the append path, writes ->next_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.","publishedAt":"2026-06-25T08:38:52.034Z","updatedAt":"2026-09-01T12:04:57.559Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"22ee4010866da81aeee08e1ea3fddbe418feb212","status":"affected","lessThan":"0e823ca0e7391630784ae7dd0981b7ad170a93d9","versionType":"git"},{"version":"543555954b1ee8d1903a7020324efb41b0c97428","status":"affected","lessThan":"c22599cc90e1cd5f8129c8670bd68a02ff7177b4","versionType":"git"},{"version":"c70df25214ac9b32b53e18e6ae3b8f073ffa6903","status":"affected","lessThan":"89b909e9704587bfecc1aab1d37e98faee03b9f9","versionType":"git"},{"version":"006a5035b495dec008805df249f92c22c89c3d2e","status":"affected","lessThan":"010c3313a4d178dc2d3ce958d2e5cb055e2864c1","versionType":"git"},{"version":"006a5035b495dec008805df249f92c22c89c3d2e","status":"affected","lessThan":"32594b09854970d7ba83eb2dc8c69a2edd158c8e","versionType":"git"},{"version":"6.12.93","status":"affected","lessThan":"6.12.94","versionType":"semver"},{"version":"6.18.3","status":"affected","lessThan":"6.18.36","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/inet_fragment.c","net/ipv4/ip_fragment.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"6.12.94","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.36","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.13","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/inet_fragment.c","net/ipv4/ip_fragment.c"]}],"references":["https://git.kernel.org/stable/c/0e823ca0e7391630784ae7dd0981b7ad170a93d9","https://git.kernel.org/stable/c/c22599cc90e1cd5f8129c8670bd68a02ff7177b4","https://git.kernel.org/stable/c/89b909e9704587bfecc1aab1d37e98faee03b9f9","https://git.kernel.org/stable/c/010c3313a4d178dc2d3ce958d2e5cb055e2864c1","https://git.kernel.org/stable/c/32594b09854970d7ba83eb2dc8c69a2edd158c8e","https://access.redhat.com/security/cve/CVE-2026-53175","https://bugzilla.redhat.com/show_bug.cgi?id=2492840","https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53175.json"],"weaknesses":["CWE-825"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/53xxx/CVE-2026-53175.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53175","state":"PUBLISHED","datePublished":"2026-06-25T08:38:52.034Z","dateUpdated":"2026-09-01T12:04:57.559Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-06-09T07:44:35.389Z"},"containers":{"cna":{"title":"inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush","descriptions":[{"lang":"en","value":"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->fragments_tail and q->last_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 ->len of\nthat pointer and, on the append path, writes ->next_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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"22ee4010866da81aeee08e1ea3fddbe418feb212","status":"affected","lessThan":"0e823ca0e7391630784ae7dd0981b7ad170a93d9","versionType":"git"},{"version":"543555954b1ee8d1903a7020324efb41b0c97428","status":"affected","lessThan":"c22599cc90e1cd5f8129c8670bd68a02ff7177b4","versionType":"git"},{"version":"c70df25214ac9b32b53e18e6ae3b8f073ffa6903","status":"affected","lessThan":"89b909e9704587bfecc1aab1d37e98faee03b9f9","versionType":"git"},{"version":"006a5035b495dec008805df249f92c22c89c3d2e","status":"affected","lessThan":"010c3313a4d178dc2d3ce958d2e5cb055e2864c1","versionType":"git"},{"version":"006a5035b495dec008805df249f92c22c89c3d2e","status":"affected","lessThan":"32594b09854970d7ba83eb2dc8c69a2edd158c8e","versionType":"git"},{"version":"6.12.93","status":"affected","lessThan":"6.12.94","versionType":"semver"},{"version":"6.18.3","status":"affected","lessThan":"6.18.36","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/inet_fragment.c","net/ipv4/ip_fragment.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"6.12.94","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.36","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.13","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/inet_fragment.c","net/ipv4/ip_fragment.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/0e823ca0e7391630784ae7dd0981b7ad170a93d9"},{"url":"https://git.kernel.org/stable/c/c22599cc90e1cd5f8129c8670bd68a02ff7177b4"},{"url":"https://git.kernel.org/stable/c/89b909e9704587bfecc1aab1d37e98faee03b9f9"},{"url":"https://git.kernel.org/stable/c/010c3313a4d178dc2d3ce958d2e5cb055e2864c1"},{"url":"https://git.kernel.org/stable/c/32594b09854970d7ba83eb2dc8c69a2edd158c8e"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - IPv4 and IPv6 fragment reassembly is reached by received network packets before transport-layer delivery, and the affected generic inet fragment code is shared by network-facing reassembly paths. A remote peer can supply the crafted fragmented traffic that reaches `inet_frag_queue_insert()`.\nAC:L - The vulnerable window is a race between a fragment that already found the queue and netns teardown flushing that queue. The race can be retried and, in attacker-controlled namespace/container scenarios, both fragmented traffic and namespace teardown/churn are attacker-controlled.\nPR:N - No authentication or capability check gates normal IPv4/IPv6 fragment receive and reassembly before the vulnerable queue insertion path. The packet-processing side is reachable pre-authentication by crafted fragmented traffic.\nUI:N - Exploitation does not require a victim user to open a file, mount anything, or perform another interactive action. Packet delivery and namespace teardown are kernel/system events.\nS:U - The corruption occurs inside the kernel network stack and impacts the same kernel security authority. This is not a guest-to-host, IOMMU, or other explicit security-scope crossing.\nC:H - The bug is a slab use-after-free involving freed `sk_buff` objects and stale queue pointers. Such memory corruption can be shaped into kernel memory disclosure primitives.\nI:H - The append path can write through the stale freed `fragments_tail` object via `next_frag`, producing kernel heap memory corruption. A UAF write primitive is sufficient to support control-flow hijack or arbitrary kernel data modification.\nA:H - Even without full exploitation, dereferencing and writing through freed skb memory can crash or oops the kernel. The fragment path can be triggered repeatedly with crafted traffic."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:33:44.673Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.93","versionEndExcluding":"6.12.94"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18.3","versionEndExcluding":"6.18.36"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.0.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"kernel: Linux kernel: Memory corruption via use-after-free in internet fragmentation","descriptions":[{"lang":"en","value":"A flaw was found in the Linux kernel's internet fragmentation code. This vulnerability, a use-after-free, occurs due to a timing issue during the shutdown of network namespaces. A local attacker could exploit this by manipulating network namespace operations, potentially leading to memory corruption. This could result in a system crash, causing a denial of service, or in some cases, allow for an increase in their access privileges."}],"affected":[{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 10","packageName":"kernel","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:10"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 6","packageName":"kernel","defaultStatus":"unknown","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:6"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 7","packageName":"kernel","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:7"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 7","packageName":"kernel-rt","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:7"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","packageName":"kernel","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:8"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","packageName":"kernel-rt","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:8"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"kernel","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"kernel-rt","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]}],"references":[{"url":"https://access.redhat.com/security/cve/CVE-2026-53175","tags":["vdb-entry","x_refsource_REDHAT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2492840","name":"RHBZ#2492840","tags":["issue-tracking","x_refsource_REDHAT"]},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53175.json","tags":["x_sadp-csaf-vex"]}],"metrics":[{"other":{"content":{"namespace":"https://access.redhat.com/security/updates/classification/","value":"Important"},"type":"Red Hat severity rating"}},{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":7,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-825","description":"Expired Pointer Dereference","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"redhat-SADP","orgId":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c","dateUpdated":"2026-09-01T12:04:57.559Z"},"datePublic":"2026-06-25T00:00:00.000Z","timeline":[{"lang":"en","time":"2026-06-25T00:00:00.000Z","value":"Reported to Red Hat."},{"lang":"en","time":"2026-06-25T00:00:00.000Z","value":"Made public."}],"x_adpType":"supplier","x_generator":{"engine":"sadp-cli 1.0.0"}}]}}}