{"id":"CVE-2026-63992","state":"PUBLISHED","title":"tunnels: do not assume transport header in iptunnel_pmtud_check_icmp()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntunnels: do not assume transport header in iptunnel_pmtud_check_icmp()\n\nIn some cases, iptunnel_pmtud_check_icmp() can be called while\nskb transport header is not set.\n\nThis triggers an out-of-bound access, because\n(typeof(skb->transport_header))~0U is 65535.\n\nAccess the icmp header based on IPv4 network header,\nafter making sure icmp->type is present in skb linear part.\n\nNote that iptunnel_pmtud_check_icmpv6()) is fine.","publishedAt":"2026-07-19T14:56:12.528Z","updatedAt":"2026-10-19T20:18:01.188Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"5a92cb45e34749865d03daf8d3500f77b5f6644c","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"c7b7ec3e69e673c0d6b57f74d21da50c485c598e","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"7f4f7efe7f30edd29c4988de01728bf2398217e4","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"a096b6e34f602950af9a2b0856cd93a5f4c276d7","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"43368636c663cff6e59dde93cf4b8e43ac28eb93","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"cb549df9ce4ee15c9d5b19ddab12cf2128e4313c","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"509323077ef79a26ba0c60bb556e45c12c398b2d","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ip_tunnel_core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.9","versionType":"semver"},{"version":"5.10.259","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ip_tunnel_core.c"]}],"references":["https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c","https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e","https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4","https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec","https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7","https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93","https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c","https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d"],"weaknesses":["CWE-125"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63992.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63992","state":"PUBLISHED","datePublished":"2026-07-19T14:56:12.528Z","dateUpdated":"2026-10-19T20:18:01.188Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.025Z"},"containers":{"cna":{"title":"tunnels: do not assume transport header in iptunnel_pmtud_check_icmp()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ntunnels: do not assume transport header in iptunnel_pmtud_check_icmp()\n\nIn some cases, iptunnel_pmtud_check_icmp() can be called while\nskb transport header is not set.\n\nThis triggers an out-of-bound access, because\n(typeof(skb->transport_header))~0U is 65535.\n\nAccess the icmp header based on IPv4 network header,\nafter making sure icmp->type is present in skb linear part.\n\nNote that iptunnel_pmtud_check_icmpv6()) is fine."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"5a92cb45e34749865d03daf8d3500f77b5f6644c","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"c7b7ec3e69e673c0d6b57f74d21da50c485c598e","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"7f4f7efe7f30edd29c4988de01728bf2398217e4","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"a096b6e34f602950af9a2b0856cd93a5f4c276d7","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"43368636c663cff6e59dde93cf4b8e43ac28eb93","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"cb549df9ce4ee15c9d5b19ddab12cf2128e4313c","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"509323077ef79a26ba0c60bb556e45c12c398b2d","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ip_tunnel_core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.9","versionType":"semver"},{"version":"5.10.259","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/ip_tunnel_core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c"},{"url":"https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e"},{"url":"https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4"},{"url":"https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec"},{"url":"https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7"},{"url":"https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93"},{"url":"https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c"},{"url":"https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","baseScore":9.1,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable code runs on the VXLAN/GENEVE transmit path when processing remotely received UDP-encapsulated tunnel traffic (or L2 frames forwarded through a bridge port), which is reachable by sending crafted packets over the network to the victim VTEP.\nAC:L - The attacker fully controls the inner IPv4 header fields (DF bit, length, addresses) and can reliably craft oversized packets that exceed the tunnel-adjusted PMTU on bridge-port tunnel devices without depending on race timing or uncontrollable system state.\nPR:N - Exploitation requires only the ability to send network packets to a host with VXLAN/GENEVE bridged; no local account, authentication, or capabilities on the victim are needed.\nUI:N - No victim user action is required; the kernel processes attacker-supplied packets automatically through the tunnel receive, bridge forward, and re-encapsulation path.\nS:U - The out-of-bounds read and resulting kernel oops occur within the kernel network stack on the same host; there is no crossing of a VM, container, or IOMMU security boundary beyond standard kernel memory safety failure.\nC:H - Reading through `icmp_hdr(skb)` when `transport_header` is unset causes an out-of-bounds read at `skb->head + 65535`, potentially disclosing adjacent kernel memory beyond the skb buffer before any bounds checking occurs.\nI:N - The flaw is an out-of-bounds read of the ICMP type field; it does not directly modify or write kernel memory, though it may cause a kernel fault.\nA:H - The invalid pointer dereference at offset 65535 can trigger a kernel oops or panic when accessing unmapped memory, causing denial of service on the affected host."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:37:55.661Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"5.10.259"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"5.15.210"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.1.176"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.6.143"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.12.93"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.18.35"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"7.0.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-63992","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:34:46.388136Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-125","lang":"en","type":"CWE","description":"CWE-125 Out-of-bounds Read"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:18:01.188Z"}}]}}}