{"id":"CVE-2026-97984","title":"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…","summary":"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…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-190"],"vendor":"Linux","product":"Linux","affected":["Linux >= 427faee167bce4ccb0b22f6815a9ac509e31d4c3 < 1dd562f3019019ffdf4b396570613053facda9ee","Linux >= 427faee167bce4ccb0b22f6815a9ac509e31d4c3 < 1d56a00ec91f2885c64ea5b8cea18cb746b91bbb","Linux >= 427faee167bce4ccb0b22f6815a9ac509e31d4c3 < ce66352d3eb21825410af8b91db7cc4bb8e22c98","Linux >= 427faee167bce4ccb0b22f6815a9ac509e31d4c3 < e01b7c176d9af2b7c22bb3fe12cf9a7904f99fdc","Linux >= 427faee167bce4ccb0b22f6815a9ac509e31d4c3 < 0ae10b6be49b425827659b23bcce498f80eb7182","Linux 5.15"],"published":"2026-09-25","updated":"2026-10-03","sourceUpdated":"2026-10-03T11:18:22.383","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-97984","references":[{"url":"https://git.kernel.org/stable/c/0ae10b6be49b425827659b23bcce498f80eb7182","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1d56a00ec91f2885c64ea5b8cea18cb746b91bbb","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1dd562f3019019ffdf4b396570613053facda9ee","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ce66352d3eb21825410af8b91db7cc4bb8e22c98","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e01b7c176d9af2b7c22bb3fe12cf9a7904f99fdc","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97984.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-97984"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2541086"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-97984"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97984"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97984.mbox"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00168,"epssPercentile":0.06037,"cvssSource":"vendor","ingestedAt":"2026-09-25T11:06:38.868Z","slug":"CVE-2026-97984","body":"## Overview\n\nIn 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\").\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Low · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10 · updated 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97984.json)","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":213303,"id":"CVE-2026-97984","ts":1790754685478,"field":"cvss","old":null,"new":"5.5"},{"seq":213302,"id":"CVE-2026-97984","ts":1790754685478,"field":"severity","old":"none","new":"medium"}]}