{"id":"CVE-2026-97984","revision":"89d871a9ea8d4fef8fccf3ed22773768","records":[{"revision":"89d871a9ea8d4fef8fccf3ed22773768","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-97984","aliases":[],"title":"net: ipv6: Fix UDP length overflow with PMTU discover and big MTU","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: Fix UDP length overflow with PMTU discover and big MTU\n\nThis commit bounds cork->base.fragsize to IP6_MAX_MTU for UDP sockets to\navoid a possible overflow of UDP length that triggers a WARN in\nudp_set_len_short when setsockopt IPV6_MTU_DISCOVER is set to\nIPV6_PMTUDISC_DO or IPV6_PMTUDISC_PROBE, and a large packet is sent over\na netdev with an unusually large MTU.\n\nSteps to reproduce (included in the new selftest):\n\n1. Set device MTU bigger than IP6_MAX_MTU. cork->base.fragsize will be\n   set to that MTU in ip6_setup_cork.\n2. Set IPV6_MTU_DISCOVER to IPV6_PMTUDISC_PROBE or IPV6_PMTUDISC_DO. It\n   lets maxnonfragsize be set to device MTU (cork->fragsize) in\n   __ip6_append_data, rather than to IP6_MAX_MTU.\n3. Send 65528 bytes of payload (+8 bytes of UDP header, +40 bytes of\n   IPv6 header). Device MTU allows it (it's only one byte bigger than\n   IP6_MAX_MTU, and the device MTU is bigger than that).\n4. The UDP length in the built packet is 65536, which overflows the\n   16-bit length field and triggers the WARN in udp_set_len_short.\n\nTo avoid breaking sending UDP jumbograms over raw IPv6 sockets, limit\nthe change to UDP sockets only.\n\nThe original overflow bug with IPv6 and IPV6_PMTUDISC_DO seems to\npredate git history (verified reproduction on 2.6.21), was fixed later,\nand then reappeared in commit 427faee167bc (\"net: ipv6: introduce\nip6_dst_mtu_maybe_forward\"), which is chosen as the Fixes tag here. The\noverflow with IPV6_PMTUDISC_PROBE reproduces since its introduction in\ncommit 628a5c561890 (\"[INET]: Add IP(V6)_PMTUDISC_RPOBE\").","state":0,"publishedAt":"2026-09-25T10:23:19.568+00:00","modifiedAt":"2026-10-19T09:11:51.31+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/ipv6/ip6_output.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"427faee167bce4ccb0b22f6815a9ac509e31d4c3\",\n                            \"lessThan\": \"1dd562f3019019ffdf4b396570613053facda9ee\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"427faee167bce4ccb0b22f6815a9ac509e31d4c3\",\n                            \"lessThan\": \"1d56a00ec91f2885c64ea5b8cea18cb746b91bbb\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"427faee167bce4ccb0b22f6815a9ac509e31d4c3\",\n                            \"lessThan\": \"ce66352d3eb21825410af8b91db7cc4bb8e22c98\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"427faee167bce4ccb0b22f6815a9ac509e31d4c3\",\n                            \"lessThan\": \"e01b7c176d9af2b7c22bb3fe12cf9a7904f99fdc\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"427faee167bce4ccb0b22f6815a9ac509e31d4c3\",\n                            \"lessThan\": \"0ae10b6be49b425827659b23bcce498f80eb7182\",\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/ipv6/ip6_output.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.15\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.15\",\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\": \"6.12.111\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.53\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.7\",\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/1dd562f3019019ffdf4b396570613053facda9ee","https://git.kernel.org/stable/c/1d56a00ec91f2885c64ea5b8cea18cb746b91bbb","https://git.kernel.org/stable/c/ce66352d3eb21825410af8b91db7cc4bb8e22c98","https://git.kernel.org/stable/c/e01b7c176d9af2b7c22bb3fe12cf9a7904f99fdc","https://git.kernel.org/stable/c/0ae10b6be49b425827659b23bcce498f80eb7182"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-97984","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-97984","identifiers":["CVE-2026-97984"]},"retained":false,"historicalAffected":[]}],"coverage":[]}