{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72421", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.927Z", "datePublished": "2026-08-15T05:56:40.466Z", "dateUpdated": "2026-08-17T05:44:01.658Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:44:01.658Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: fib: Don't ignore error route in local/main tables.\n\nWhen CONFIG_IP_MULTIPLE_TABLES is enabled but no rule is added,\nfib_lookup() performs route lookup directly on two tables.\n\nSince the first lookup does not properly bail out, the result\nof an error route in the merged local/main table could be\noverwritten by another route in the default table:\n\n # unshare -n\n # ip link set lo up\n # ip route add 192.168.0.0/24 dev lo table 253\n # ip route add unreachable 192.168.0.0/24\n # ip route get 192.168.0.1\n 192.168.0.1 dev lo table default uid 0\n cache \n\nOnce a random rule is added, the error route is respected:\n\n # ip rule add table 0\n # ip rule del table 0\n # ip route get 192.168.0.1\n RTNETLINK answers: No route to host\n\nLet's fix the inconsistent behaviour." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N", "baseScore": 10, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - fib_lookup() is on the IPv4 receive and transmit datapaths (ip_route_input_rcu, ip_route_output_key, forwarding) reached by remote packets on internet-facing routers, gateways, cloud hosts, and container nodes without any local syscall.\nAC:L - Once main/local holds an error route and default has an overlapping prefix (reproduced in the fix commit with basic ip-route commands), any matching packet or socket lookup deterministically hits the bypass; no race or attacker-independent memory layout is required.\nPR:N - Overlapping table layout is a deployment/CAP_NET_ADMIN prerequisite, but exploitation only requires sending traffic or using sockets; the remote attacker needs no credentials or privileges on the victim once the vulnerable routing state exists.\nUI:N - Route resolution runs automatically in the kernel networking stack during normal packet forwarding and connection setup; no victim mount, click, or file open is needed beyond ordinary network use.\nS:C - Bypassing unreachable/prohibit/blackhole routes can defeat network-namespace/pod egress blackholes and segmentation boundaries on multi-tenant hosts and routers, allowing access outside the intended isolated security scope.\nC:H - Ignored error routes let traffic reach destinations deliberately isolated (internal networks, metadata endpoints, sinkholed ranges), exposing data that routing policy was designed to keep inaccessible.\nI:H - Packets that should be dropped or rejected are instead forwarded via the default-table route, enabling injection of traffic into networks marked unreachable, prohibited, or blackhole.\nA:N - The defect is incorrect route selection only; it does not corrupt memory, panic the kernel, deadlock, or inherently exhaust resources, so availability impact is none." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/ip_fib.h" ], "versions": [ { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "a29e95fbc51e8a1b932773fd0e259b2080881443", "status": "affected", "versionType": "git" }, { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "5ae18d87a45698e8244d0fcba64c658c35a7dd3d", "status": "affected", "versionType": "git" }, { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "9127589aabdee588278e8d0d0bd3709a760a92c8", "status": "affected", "versionType": "git" }, { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "49eaf1403201357762d745a35882fb734107d763", "status": "affected", "versionType": "git" }, { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "fd25996f57a95d56bc568c89b4921edcf334b7d8", "status": "affected", "versionType": "git" }, { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "828fad4fd418bcdb9f5d66fec0d184c52a85ec31", "status": "affected", "versionType": "git" }, { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "a668fa160247d7bbe921548cb845f607b8b9305f", "status": "affected", "versionType": "git" }, { "version": "f4530fa574df4d833506c53697ed1daa0d390bf4", "lessThan": "b72f0db64205d9ce462038ba995d5d31eff32dc1", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/ip_fib.h" ], "versions": [ { "version": "3.6", "status": "affected" }, { "version": "0", "lessThan": "3.6", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "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": "3.6", "versionEndExcluding": "5.10.261" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a29e95fbc51e8a1b932773fd0e259b2080881443" }, { "url": "https://git.kernel.org/stable/c/5ae18d87a45698e8244d0fcba64c658c35a7dd3d" }, { "url": "https://git.kernel.org/stable/c/9127589aabdee588278e8d0d0bd3709a760a92c8" }, { "url": "https://git.kernel.org/stable/c/49eaf1403201357762d745a35882fb734107d763" }, { "url": "https://git.kernel.org/stable/c/fd25996f57a95d56bc568c89b4921edcf334b7d8" }, { "url": "https://git.kernel.org/stable/c/828fad4fd418bcdb9f5d66fec0d184c52a85ec31" }, { "url": "https://git.kernel.org/stable/c/a668fa160247d7bbe921548cb845f607b8b9305f" }, { "url": "https://git.kernel.org/stable/c/b72f0db64205d9ce462038ba995d5d31eff32dc1" } ], "title": "ipv4: fib: Don't ignore error route in local/main tables.", "x_generator": { "engine": "bippy-1.2.0" } } } }