{"id":"CVE-2026-63993","state":"PUBLISHED","title":"vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()\n\nskb_tunnel_check_pmtu() can change skb->head.\n\nReusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.\n\nUse instead ip_hdr(skb) as done in drivers/net/bareudp.c\nand drivers/net/geneve.c.\n\nFound by Sashiko.","publishedAt":"2026-07-19T14:56:13.218Z","updatedAt":"2026-10-19T20:18:01.347Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"6b8bfce9d2f774d2c2243e0248e03efb99bba6c0","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"9257f56ac47ef1976bcd056cf986a9988eeec67a","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"8d435d68d71fb875876b722f4136caf74f2f48bd","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"dc3bfa050f873371e745bdf478b1f5b738e5733d","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"609e63312c29aad18026a1d3222e123d4b6b0feb","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"5303925e360527243b46a440a04667826bbc72b7","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"a493efd4336cf19122ae0e4cbb3d31b32d70deea","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"7d9ef0cb271555d8cf39fefe6c981e1493b25ecf","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/vxlan/vxlan_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":["drivers/net/vxlan/vxlan_core.c"]}],"references":["https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0","https://git.kernel.org/stable/c/9257f56ac47ef1976bcd056cf986a9988eeec67a","https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd","https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d","https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb","https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7","https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea","https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63993.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63993","state":"PUBLISHED","datePublished":"2026-07-19T14:56:13.218Z","dateUpdated":"2026-10-19T20:18:01.347Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.025Z"},"containers":{"cna":{"title":"vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()\n\nskb_tunnel_check_pmtu() can change skb->head.\n\nReusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.\n\nUse instead ip_hdr(skb) as done in drivers/net/bareudp.c\nand drivers/net/geneve.c.\n\nFound by Sashiko."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"6b8bfce9d2f774d2c2243e0248e03efb99bba6c0","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"9257f56ac47ef1976bcd056cf986a9988eeec67a","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"8d435d68d71fb875876b722f4136caf74f2f48bd","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"dc3bfa050f873371e745bdf478b1f5b738e5733d","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"609e63312c29aad18026a1d3222e123d4b6b0feb","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"5303925e360527243b46a440a04667826bbc72b7","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"a493efd4336cf19122ae0e4cbb3d31b32d70deea","versionType":"git"},{"version":"4cb47a8644cc9eb8ec81190a50e79e6530d0297f","status":"affected","lessThan":"7d9ef0cb271555d8cf39fefe6c981e1493b25ecf","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/vxlan/vxlan_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":["drivers/net/vxlan/vxlan_core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0"},{"url":"https://git.kernel.org/stable/c/9257f56ac47ef1976bcd056cf986a9988eeec67a"},{"url":"https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd"},{"url":"https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d"},{"url":"https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb"},{"url":"https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7"},{"url":"https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea"},{"url":"https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - The bug is in VXLAN transmit processing reached when network-originated packets are decapsulated, bridged, and re-encapsulated; VXLAN is a UDP-based overlay protocol reachable from remote peers over the network.\nAC:L - An attacker can reliably trigger the bug by sending crafted oversized inner IPv4/IPv6 packets (e.g., with DF set or ICMP/ICMPv6 payloads) through a bridged VXLAN interface to force skb_tunnel_check_pmtu() to reallocate skb->head yet return 0, leaving the cached ip_hdr pointer stale.\nPR:N - Exploitation requires only the ability to send VXLAN/inner IP traffic to a host with an active VXLAN bridge port; no local account, capabilities, or authentication on the victim is needed.\nUI:N - No victim user action is required beyond normal network operation; triggering the bug is entirely driven by attacker-supplied packets forwarded through the VXLAN device.\nS:U - The vulnerability corrupts kernel heap memory on the host processing the VXLAN traffic; impact remains within the kernel's security authority and does not inherently cross a VM or sandbox boundary.\nC:H - This is a use-after-free where ip_tunnel_ecn_encap() reads from a freed skb head via the stale cached ip_hdr pointer, enabling kernel memory disclosure and supporting further exploitation.\nI:H - Use-after-free on skb data provides a foundation for heap grooming and arbitrary memory write primitives that could be leveraged for kernel code execution or privilege escalation.\nA:H - The UAF can cause kernel oops/panic during transmit processing and is independently exploitable for denial of service even when full code execution is not achieved."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:37:57.287Z"},"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-2026-63993","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:34:49.188699Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","type":"CWE","description":"CWE-416 Use After Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:18:01.347Z"}}]}}}