{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-53175", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-53175" ], "published": "2026-06-25T08:41:40Z", "summary": "inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush", "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->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.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.12.93-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.12.93+rpt-rpi-2712", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v6", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v7", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v7l", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v8", "binary_version": "1:6.12.93-1+rpt1" }, { "binary_name": "linux-image-6.12.93+rpt-rpi-v8-rt", "binary_version": "1:6.12.93-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.12.93-1+rpt1": { "linux_commit": "d8ab4e908235da7727f22dd36ad5af224671677d", "upstream_version": "6.12.93", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.12.94" } } } }, { "package": { "ecosystem": "Raspberry Pi OS:13", "name": "linux" }, "versions": [ "1:6.18.29-1+rpt1", "1:6.18.33-1+rpt1", "1:6.18.34-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.18.29+rpt-rpi-2712", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v6", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v7", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-2712", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v6", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v7", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8-rt", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-2712", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v6", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v7", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8-rt", "binary_version": "1:6.18.34-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.36" }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.36" }, "1:6.18.34-1+rpt1": { "linux_commit": "c8c7494100e99ee05b11aaa4f0588a223a63d1af", "upstream_version": "6.18.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.36" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-53175" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/0e823ca0e7391630784ae7dd0981b7ad170a93d9" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/c22599cc90e1cd5f8129c8670bd68a02ff7177b4" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/89b909e9704587bfecc1aab1d37e98faee03b9f9" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/010c3313a4d178dc2d3ce958d2e5cb055e2864c1" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/32594b09854970d7ba83eb2dc8c69a2edd158c8e" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 9.8, "cvss_v3_severity": "Critical", "scenario": "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." } } }