{"api_version":"1","generated_at":"2026-10-21T18:42:58+00:00","cve":"CVE-2026-98541","urls":{"html":"https://cve.report/CVE-2026-98541","api":"https://cve.report/api/cve/CVE-2026-98541.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98541","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98541"},"summary":{"title":"fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT","description":"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).","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-18 16:17:05","updated_at":"2026-10-18 16:17:05"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/3bcc1624cc1cdcc05b566475d6e848093ab2a8f6","name":"https://git.kernel.org/stable/c/3bcc1624cc1cdcc05b566475d6e848093ab2a8f6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/7f4ba56f5d310dd018972916167985010a5d66a1","name":"https://git.kernel.org/stable/c/7f4ba56f5d310dd018972916167985010a5d66a1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/46b1ffb7e169c7e401dd890b29e55dbc261f8f01","name":"https://git.kernel.org/stable/c/46b1ffb7e169c7e401dd890b29e55dbc261f8f01","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d22609f3d13fc5baacd92c222731b03c593401db","name":"https://git.kernel.org/stable/c/d22609f3d13fc5baacd92c222731b03c593401db","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/fd20220f86947d66d4dba2d76f13a28dbd86ef30","name":"https://git.kernel.org/stable/c/fd20220f86947d66d4dba2d76f13a28dbd86ef30","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221","name":"https://git.kernel.org/stable/c/520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8b43f40798bb2758489fbbcae7e841ad4443c213","name":"https://git.kernel.org/stable/c/8b43f40798bb2758489fbbcae7e841ad4443c213","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b1229b210ef5a39c58be665e6798203751411842","name":"https://git.kernel.org/stable/c/b1229b210ef5a39c58be665e6798203751411842","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98541","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98541","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 fd20220f86947d66d4dba2d76f13a28dbd86ef30 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 46b1ffb7e169c7e401dd890b29e55dbc261f8f01 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 7f4ba56f5d310dd018972916167985010a5d66a1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 3bcc1624cc1cdcc05b566475d6e848093ab2a8f6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 8b43f40798bb2758489fbbcae7e841ad4443c213 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 b1229b210ef5a39c58be665e6798203751411842 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 d22609f3d13fc5baacd92c222731b03c593401db git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.18","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.18 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.10.271 5.10.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.222 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.189 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.158 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.112 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.55 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.9 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/ipv4/fou_core.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"fd20220f86947d66d4dba2d76f13a28dbd86ef30","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"},{"lessThan":"46b1ffb7e169c7e401dd890b29e55dbc261f8f01","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"},{"lessThan":"7f4ba56f5d310dd018972916167985010a5d66a1","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"},{"lessThan":"3bcc1624cc1cdcc05b566475d6e848093ab2a8f6","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"},{"lessThan":"8b43f40798bb2758489fbbcae7e841ad4443c213","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"},{"lessThan":"b1229b210ef5a39c58be665e6798203751411842","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"},{"lessThan":"520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"},{"lessThan":"d22609f3d13fc5baacd92c222731b03c593401db","status":"affected","version":"23461551c00628c3f3fe9cf837bf53cf8f212b63","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/ipv4/fou_core.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":"5.10.271","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.222","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.189","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.158","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.112","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.55","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.271","versionStartIncluding":"3.18","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.222","versionStartIncluding":"3.18","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.189","versionStartIncluding":"3.18","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.158","versionStartIncluding":"3.18","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.112","versionStartIncluding":"3.18","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.55","versionStartIncluding":"3.18","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.9","versionStartIncluding":"3.18","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"3.18","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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)."}],"providerMetadata":{"dateUpdated":"2026-10-19T09:21:24.620Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/fd20220f86947d66d4dba2d76f13a28dbd86ef30"},{"url":"https://git.kernel.org/stable/c/46b1ffb7e169c7e401dd890b29e55dbc261f8f01"},{"url":"https://git.kernel.org/stable/c/7f4ba56f5d310dd018972916167985010a5d66a1"},{"url":"https://git.kernel.org/stable/c/3bcc1624cc1cdcc05b566475d6e848093ab2a8f6"},{"url":"https://git.kernel.org/stable/c/8b43f40798bb2758489fbbcae7e841ad4443c213"},{"url":"https://git.kernel.org/stable/c/b1229b210ef5a39c58be665e6798203751411842"},{"url":"https://git.kernel.org/stable/c/520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221"},{"url":"https://git.kernel.org/stable/c/d22609f3d13fc5baacd92c222731b03c593401db"}],"title":"fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98541","datePublished":"2026-10-18T15:18:09.190Z","dateReserved":"2026-09-25T10:25:14.356Z","dateUpdated":"2026-10-19T09:21:24.620Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-18 16:17:05","lastModifiedDate":"2026-10-18 16:17:05","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98541","Ordinal":"1","Title":"fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT","CVE":"CVE-2026-98541","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98541","Ordinal":"1","NoteData":"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).","Type":"Description","Title":"fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT"}]}}}