{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74583", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.918Z", "datePublished": "2026-08-21T16:31:55.886Z", "dateUpdated": "2026-10-16T19:05:58.388Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-25T05:40:10.077Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_route: fix fastmap use-after-free on filter\n\nThe route4 classifier maintains a 16-slot fastmap cache that stores raw\nstruct route4_filter pointers indexed by (id, iif). The reader\n(route4_classify) populates this cache via route4_set_fastmap() for every\nclassified packet that hits a filter. The writer (route4_delete,\nroute4_change) clears the cache via route4_reset_fastmap() before\nRCU-deferred kfree of the filter.\n\nThis creates a UAF race:\n 1. Reader walks the RCU-protected bucket chain, finds filter f\n 2. Writer unlinks f, calls route4_reset_fastmap(), then tcf_queue_work()\n 3. Reader calls route4_set_fastmap() and writes f into the cache\n *after* the writer's reset, caching a pointer about to be freed\n 4. After the RCU grace period, kfree(f) executes\n 5. Next classified packet on the same (id, iif) tuple hits the stale\n fastmap entry and reads f->res from freed memory\n\nReproduced with an mdelay(100) accelerator in route4_set_fastmap() and a\nconcurrent add/delete stress test (provided by both zdi and Santosh).\nBoth triggered KASAN slab-use-after-free reports in the route4 fastmap\npaths.\n\nFix:\nIntroduce a per-filter boolean dying flag to suppress stale fastmap\nrepublishing by in-flight readers." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploitation requires local rtnetlink RTM_NEWTFILTER/RTM_DELTFILTER (tc filter add/change/del route) through sendmsg→rtnetlink_rcv_msg→tc_new_tfilter/tc_del_tfilter→route4_change/route4_delete; remote packets alone cannot trigger the filter-deletion side of the race.\nAC:L - The attacker controls both race sides—concurrent route filter add/change/delete via netlink plus traffic through route4_classify on clsact/ingress/egress qdiscs; ZDI and independent reporter stress tests reproduced KASAN slab-use-after-free without uncontrollable prerequisites.\nPR:L - Non-GET rtnetlink handlers require netlink_net_capable(CAP_NET_ADMIN), evaluated against the target network namespace user_ns; an unprivileged local user obtains CAP_NET_ADMIN via user+network namespaces (unshare -Urn) and configures clsact with route filters.\nUI:N - No victim interaction is needed; the attacker configures the route classifier, drives concurrent filter churn, and generates matching traffic from their own processes.\nS:U - Impact is kernel memory corruption within the same kernel security boundary (local privilege escalation/DoS); it does not cross VM, hypervisor, or IOMMU boundaries.\nC:H - Slab use-after-free: a stale fastmap entry retains a freed route4_filter pointer and route4_classify dereferences f->res from freed kmalloc memory; KASAN confirmed slab-use-after-free, enabling arbitrary kernel read via heap reclaim/spray.\nI:H - UAF of the kmalloc route4_filter object allows attacker-controlled heap spraying to reclaim the freed slot and obtain write/control-flow hijacking primitives; memory corruption is exploitable beyond a simple crash.\nA:H - UAF on the fastmap hot path causes kernel oops/panic under concurrent filter churn; KASAN slab-use-after-free was confirmed during add/delete stress testing, providing reliable denial of service even without full exploitation." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/cls_route.c" ], "versions": [ { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "7897198b26445b4009a057bda1986b94a99e5d5f", "status": "affected", "versionType": "git" }, { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "820f083c294ad6d319c02a7d43294f2ed2565139", "status": "affected", "versionType": "git" }, { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "5ec9001be6d0eb527251125632ec8fe88278897f", "status": "affected", "versionType": "git" }, { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "b969984b2bdc85d721ce4047cd270cd37ec705a2", "status": "affected", "versionType": "git" }, { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "a17f636c9330eac879822ce29f998e5abd1b72c1", "status": "affected", "versionType": "git" }, { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "0e7a8cf8895b06d07c7311f028eba16ad742b9bc", "status": "affected", "versionType": "git" }, { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "ae9aff87025219005a2d16b4fe83d6f24643e50d", "status": "affected", "versionType": "git" }, { "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "lessThan": "47d7f7051253bdc02b1d245d87e38f16d31a74df", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/cls_route.c" ], "versions": [ { "version": "3.18", "status": "affected" }, { "version": "0", "lessThan": "3.18", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.265", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.216", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.183", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.152", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.104", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.45", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.9", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "5.10.265" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "5.15.216" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "6.1.183" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "6.6.152" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "6.12.104" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "6.18.45" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "7.1.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.18", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/7897198b26445b4009a057bda1986b94a99e5d5f" }, { "url": "https://git.kernel.org/stable/c/820f083c294ad6d319c02a7d43294f2ed2565139" }, { "url": "https://git.kernel.org/stable/c/5ec9001be6d0eb527251125632ec8fe88278897f" }, { "url": "https://git.kernel.org/stable/c/b969984b2bdc85d721ce4047cd270cd37ec705a2" }, { "url": "https://git.kernel.org/stable/c/a17f636c9330eac879822ce29f998e5abd1b72c1" }, { "url": "https://git.kernel.org/stable/c/0e7a8cf8895b06d07c7311f028eba16ad742b9bc" }, { "url": "https://git.kernel.org/stable/c/ae9aff87025219005a2d16b4fe83d6f24643e50d" }, { "url": "https://git.kernel.org/stable/c/47d7f7051253bdc02b1d245d87e38f16d31a74df" } ], "title": "net/sched: cls_route: fix fastmap use-after-free on filter", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-74583", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:01:17.964713Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:05:58.388Z" } } ] } }