{"schema":"threatline.record/2","record":{"id":"CVE-2026-97984","aliases":[],"summary":"net: ipv6: Fix UDP length overflow with PMTU discover and big MTU","details":"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\").","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-97984","source_modified_at":"2026-10-19T09:11:51.310Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"427faee167bce4ccb0b22f6815a9ac509e31d4c3","lessThan":"1dd562f3019019ffdf4b396570613053facda9ee","status":"affected","versionType":"git"},{"version":"427faee167bce4ccb0b22f6815a9ac509e31d4c3","lessThan":"1d56a00ec91f2885c64ea5b8cea18cb746b91bbb","status":"affected","versionType":"git"},{"version":"427faee167bce4ccb0b22f6815a9ac509e31d4c3","lessThan":"ce66352d3eb21825410af8b91db7cc4bb8e22c98","status":"affected","versionType":"git"},{"version":"427faee167bce4ccb0b22f6815a9ac509e31d4c3","lessThan":"e01b7c176d9af2b7c22bb3fe12cf9a7904f99fdc","status":"affected","versionType":"git"},{"version":"427faee167bce4ccb0b22f6815a9ac509e31d4c3","lessThan":"0ae10b6be49b425827659b23bcce498f80eb7182","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-97984","source_modified_at":"2026-10-19T09:11:51.310Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"5.15","status":"affected"},{"version":"0","lessThan":"5.15","status":"unaffected","versionType":"semver"},{"version":"6.6.158","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.111","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.53","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.7","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-2026-97984","source_modified_at":"2026-10-19T09:11:51.310Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"1dd562f3019019ffdf4b396570613053facda9ee","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-97984","source_modified_at":"2026-10-19T09:11:51.310Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"1d56a00ec91f2885c64ea5b8cea18cb746b91bbb","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-97984","source_modified_at":"2026-10-19T09:11:51.310Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"0ae10b6be49b425827659b23bcce498f80eb7182","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00168,"percentile":0.05717,"score_date":"2026-10-23"},"published_at":"2026-09-25T10:23:19.568Z","modified_at":"2026-10-19T09:11:51.310Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-97984","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T09:11:51.310Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-97984","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/1dd562f3019019ffdf4b396570613053facda9ee"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/1d56a00ec91f2885c64ea5b8cea18cb746b91bbb"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/ce66352d3eb21825410af8b91db7cc4bb8e22c98"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/e01b7c176d9af2b7c22bb3fe12cf9a7904f99fdc"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/0ae10b6be49b425827659b23bcce498f80eb7182"}],"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":"2026-10-19T09:11:51.310Z","content_hash":"e0ef4222c7dfe637d2682f92f90b9720d0c3b8cd574c64c5d30c71eb679f4418"}}