{"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": "2026-08-21T16:31:55.886Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-21T16:31:55.886Z"}, "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."}], "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"}, 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"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": 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"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"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/sched/cls_route.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "7897198b26445b4009a057bda1986b94a99e5d5f", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}, {"lessThan": "820f083c294ad6d319c02a7d43294f2ed2565139", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}, {"lessThan": "5ec9001be6d0eb527251125632ec8fe88278897f", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}, {"lessThan": "b969984b2bdc85d721ce4047cd270cd37ec705a2", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}, {"lessThan": "a17f636c9330eac879822ce29f998e5abd1b72c1", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}, {"lessThan": "0e7a8cf8895b06d07c7311f028eba16ad742b9bc", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}, {"lessThan": "ae9aff87025219005a2d16b4fe83d6f24643e50d", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}, {"lessThan": "47d7f7051253bdc02b1d245d87e38f16d31a74df", "status": "affected", "version": "1109c00547fc66df45b9ff923544be4c1e1bec13", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["net/sched/cls_route.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "3.18"}, {"lessThan": "3.18", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.265", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.216", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.183", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.152", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.104", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.45", "versionType": "semver"}, {"lessThanOrEqual": "7.1.*", "status": "unaffected", "version": "7.1.9", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.2", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "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."}], "id": "CVE-2026-74583", "lastModified": "2026-08-21T17:16:44.643", "metrics": {}, "published": "2026-08-21T17:16:44.643", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/0e7a8cf8895b06d07c7311f028eba16ad742b9bc"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/47d7f7051253bdc02b1d245d87e38f16d31a74df"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/5ec9001be6d0eb527251125632ec8fe88278897f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/7897198b26445b4009a057bda1986b94a99e5d5f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/820f083c294ad6d319c02a7d43294f2ed2565139"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a17f636c9330eac879822ce29f998e5abd1b72c1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ae9aff87025219005a2d16b4fe83d6f24643e50d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/b969984b2bdc85d721ce4047cd270cd37ec705a2"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: net/sched: cls_route: fix fastmap use-after-free on filter", "id": "2521054", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2521054"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-825", "details": ["A flaw was found in the Linux kernel's `net/sched: cls_route` component. A race condition exists in the `route4` classifier's fastmap cache, where a reader can re-cache a pointer to a filter that has already been freed by a writer. This can lead to a use-after-free condition, allowing subsequent packet classifications to read from freed memory. The most important consequence is memory corruption, which can result in system instability or a denial of service."], "name": "CVE-2026-74583", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-08-21T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-74583\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-74583\nhttps://lore.kernel.org/linux-cve-announce/2026082100-CVE-2026-74583-70cb@gregkh/T"], "threat_severity": "Moderate"}

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