{"id":"CVE-2026-98541","revision":"a1348b8421fe4e18a4e195b73469eabe","records":[{"revision":"a1348b8421fe4e18a4e195b73469eabe","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-98541","aliases":[],"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":0,"publishedAt":"2026-10-18T15:18:09.19+00:00","modifiedAt":"2026-10-19T09:21:24.62+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/ipv4/fou_core.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"fd20220f86947d66d4dba2d76f13a28dbd86ef30\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"46b1ffb7e169c7e401dd890b29e55dbc261f8f01\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"7f4ba56f5d310dd018972916167985010a5d66a1\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"3bcc1624cc1cdcc05b566475d6e848093ab2a8f6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"8b43f40798bb2758489fbbcae7e841ad4443c213\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"b1229b210ef5a39c58be665e6798203751411842\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"23461551c00628c3f3fe9cf837bf53cf8f212b63\",\n                            \"lessThan\": \"d22609f3d13fc5baacd92c222731b03c593401db\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/ipv4/fou_core.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"3.18\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"3.18\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.271\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.222\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.189\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.158\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.112\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.55\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.9\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/fd20220f86947d66d4dba2d76f13a28dbd86ef30","https://git.kernel.org/stable/c/46b1ffb7e169c7e401dd890b29e55dbc261f8f01","https://git.kernel.org/stable/c/7f4ba56f5d310dd018972916167985010a5d66a1","https://git.kernel.org/stable/c/3bcc1624cc1cdcc05b566475d6e848093ab2a8f6","https://git.kernel.org/stable/c/8b43f40798bb2758489fbbcae7e841ad4443c213","https://git.kernel.org/stable/c/b1229b210ef5a39c58be665e6798203751411842","https://git.kernel.org/stable/c/520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221","https://git.kernel.org/stable/c/d22609f3d13fc5baacd92c222731b03c593401db"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98541","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98541","identifiers":["CVE-2026-98541"]},"retained":false,"historicalAffected":[]}],"coverage":[]}