{"schema":"threatline.record/2","record":{"id":"CVE-2026-98541","aliases":[],"summary":"fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT\n\nCommit 7a9bc9e3f423 (\"fou: Don't allow 0 for FOU_ATTR_IPPROTO.\") added\nNLA_POLICY_MIN(NLA_U8, 1) to fou_nl_policy[FOU_ATTR_IPPROTO], which\nrejects an explicitly supplied FOU_ATTR_IPPROTO == 0 attribute with\n-ERANGE.\n\nHowever, FOU_ATTR_IPPROTO is an optional netlink attribute. When a user\nsends FOU_CMD_ADD with FOU_ATTR_TYPE set to FOU_ENCAP_DIRECT and omits\nFOU_ATTR_IPPROTO entirely, nla_policy validation succeeds and\nparse_nl_config() leaves cfg->protocol as 0 (from memset(cfg, 0,\nsizeof(*cfg))). fou_create() then creates a FOU_ENCAP_DIRECT socket with\nfou->protocol == 0.\n\nIn fou_udp_recv(), returning -fou->protocol to udp_queue_rcv_one_skb()\ntriggers IP protocol resubmission when fou->protocol > 0, whereas\nreturning 0 tells the UDP tunnel layer that the skb was consumed without\nfreeing it. When fou->protocol == 0, every packet received on the socket\nreturns 0 from fou_udp_recv() and leaks the sk_buff.\n\nReject FOU_ENCAP_DIRECT when !cfg->protocol in fou_create() so that\ncreating a direct encapsulation port without FOU_ATTR_IPPROTO fails with\n-EINVAL while leaving FOU_CMD_DEL and FOU_CMD_GET (which share\nparse_nl_config()) unaffected.\n\nTested in QEMU against Linux 7.3.0-rc3 by sending a FOU_CMD_ADD Generic\nNetlink request with FOU_ATTR_PORT = 5555 and FOU_ATTR_TYPE =\nFOU_ENCAP_DIRECT while omitting FOU_ATTR_IPPROTO. On the unfixed kernel,\nFOU_CMD_ADD succeeds (err = 0), FOU_CMD_GET reports fou->type = 1 and\nfou->protocol = 0, and sending 4000 UDP packets to 127.0.0.1:5555 leaks\nall 4000 sk_buffs (SUnreclaim in /proc/meminfo grows from 41456 kB to\n59008 kB, +17552 kB); with this patch applied, FOU_CMD_ADD is rejected\nwith -EINVAL (-22).","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","source_modified_at":"2026-10-19T09:21:24.620Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"fd20220f86947d66d4dba2d76f13a28dbd86ef30","status":"affected","versionType":"git"},{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"46b1ffb7e169c7e401dd890b29e55dbc261f8f01","status":"affected","versionType":"git"},{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"7f4ba56f5d310dd018972916167985010a5d66a1","status":"affected","versionType":"git"},{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"3bcc1624cc1cdcc05b566475d6e848093ab2a8f6","status":"affected","versionType":"git"},{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"8b43f40798bb2758489fbbcae7e841ad4443c213","status":"affected","versionType":"git"},{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"b1229b210ef5a39c58be665e6798203751411842","status":"affected","versionType":"git"},{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221","status":"affected","versionType":"git"},{"version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","lessThan":"d22609f3d13fc5baacd92c222731b03c593401db","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","source_modified_at":"2026-10-19T09:21:24.620Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"3.18","status":"affected"},{"version":"0","lessThan":"3.18","status":"unaffected","versionType":"semver"},{"version":"5.10.271","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.222","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.189","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.158","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.112","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.55","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.9","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","source_modified_at":"2026-10-19T09:21:24.620Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"46b1ffb7e169c7e401dd890b29e55dbc261f8f01","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","source_modified_at":"2026-10-19T09:21:24.620Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"7f4ba56f5d310dd018972916167985010a5d66a1","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","source_modified_at":"2026-10-19T09:21:24.620Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"3bcc1624cc1cdcc05b566475d6e848093ab2a8f6","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","source_modified_at":"2026-10-19T09:21:24.620Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"8b43f40798bb2758489fbbcae7e841ad4443c213","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","source_modified_at":"2026-10-19T09:21:24.620Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.0021,"percentile":0.10715,"score_date":"2026-10-23"},"published_at":"2026-10-18T15:18:09.190Z","modified_at":"2026-10-19T09:21:24.620Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T09:21:24.620Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98541","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/fd20220f86947d66d4dba2d76f13a28dbd86ef30"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/46b1ffb7e169c7e401dd890b29e55dbc261f8f01"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/7f4ba56f5d310dd018972916167985010a5d66a1"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/3bcc1624cc1cdcc05b566475d6e848093ab2a8f6"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/8b43f40798bb2758489fbbcae7e841ad4443c213"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/b1229b210ef5a39c58be665e6798203751411842"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/d22609f3d13fc5baacd92c222731b03c593401db"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-19T09:21:24.620Z","content_hash":"03bb08557d27c7b12cc3bdda0d3cadd6c6a1c825f30b50df16ddc0ae2c05c7d1"}}