{"id":"CVE-2026-99041","state":"PUBLISHED","title":"ip6_gre: remove obsolete ERSPAN PMTU update","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6_gre: remove obsolete ERSPAN PMTU update\n\nA tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb,\nand mirred can redirect it to a native ip6erspan device. The legacy PMTU\nupdate in ip6erspan_tunnel_xmit() treats that metadata dst as a route.\nSince it has no output device, dst_dev(dst)->mtu dereferences NULL.\n\nOn v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used\nself-created user and network namespaces to trigger:\n\n  KASAN: null-ptr-deref\n  RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nThe update is obsolete. Commit fe1a4ca0a2b7 (\"ip6_gre: process toobig\nin a better way\") changed IPv6 GRE Too Big handling to update the\nunderlay route and removed the equivalent block from __gre6_xmit().\nip6_tnl_xmit() then propagates the underlay PMTU to the overlay route.\n\nRemove the stale ERSPAN copy and its now-unused dst variable. This\neliminates the metadata-dst dereference and keeps ERSPAN aligned with\nIPv6 GRE PMTU handling.","publishedAt":"2026-10-23T12:22:00.403Z","updatedAt":"2026-10-30T12:41:14.790Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"2e151c74bcc53e3ed313bd1c21b0d5bb442edbc0","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"ba72ed1c8476ce68eb7152dfcbc5330cefcbaa91","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"b14a682ad7d45345701e08f9279d483a1da8b36c","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"f5b143f4cd3fb7673df8d727550478a4b762908a","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"2d06cb25a497d3a7034ef9d172626c2d6620a0f1","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"8f27260b989f488760289276377db24fbfb20bfa","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"8bc60db48e8cba35488bbd6e1f94aa990afa275a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_gre.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.16","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.58","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_gre.c"]}],"references":["https://git.kernel.org/stable/c/2e151c74bcc53e3ed313bd1c21b0d5bb442edbc0","https://git.kernel.org/stable/c/ba72ed1c8476ce68eb7152dfcbc5330cefcbaa91","https://git.kernel.org/stable/c/b14a682ad7d45345701e08f9279d483a1da8b36c","https://git.kernel.org/stable/c/f5b143f4cd3fb7673df8d727550478a4b762908a","https://git.kernel.org/stable/c/2d06cb25a497d3a7034ef9d172626c2d6620a0f1","https://git.kernel.org/stable/c/8f27260b989f488760289276377db24fbfb20bfa","https://git.kernel.org/stable/c/8bc60db48e8cba35488bbd6e1f94aa990afa275a"],"weaknesses":[],"ingestedAt":"2026-10-30T13:02:04.640Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/99xxx/CVE-2026-99041.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99041","state":"PUBLISHED","datePublished":"2026-10-23T12:22:00.403Z","dateUpdated":"2026-10-30T12:41:14.790Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.387Z"},"containers":{"cna":{"title":"ip6_gre: remove obsolete ERSPAN PMTU update","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6_gre: remove obsolete ERSPAN PMTU update\n\nA tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb,\nand mirred can redirect it to a native ip6erspan device. The legacy PMTU\nupdate in ip6erspan_tunnel_xmit() treats that metadata dst as a route.\nSince it has no output device, dst_dev(dst)->mtu dereferences NULL.\n\nOn v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used\nself-created user and network namespaces to trigger:\n\n  KASAN: null-ptr-deref\n  RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nThe update is obsolete. Commit fe1a4ca0a2b7 (\"ip6_gre: process toobig\nin a better way\") changed IPv6 GRE Too Big handling to update the\nunderlay route and removed the equivalent block from __gre6_xmit().\nip6_tnl_xmit() then propagates the underlay PMTU to the overlay route.\n\nRemove the stale ERSPAN copy and its now-unused dst variable. This\neliminates the metadata-dst dereference and keeps ERSPAN aligned with\nIPv6 GRE PMTU handling."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"2e151c74bcc53e3ed313bd1c21b0d5bb442edbc0","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"ba72ed1c8476ce68eb7152dfcbc5330cefcbaa91","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"b14a682ad7d45345701e08f9279d483a1da8b36c","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"f5b143f4cd3fb7673df8d727550478a4b762908a","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"2d06cb25a497d3a7034ef9d172626c2d6620a0f1","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"8f27260b989f488760289276377db24fbfb20bfa","versionType":"git"},{"version":"5a963eb61b7c39e6c422b6e48619d19d04719358","status":"affected","lessThan":"8bc60db48e8cba35488bbd6e1f94aa990afa275a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_gre.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.16","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.58","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_gre.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2e151c74bcc53e3ed313bd1c21b0d5bb442edbc0"},{"url":"https://git.kernel.org/stable/c/ba72ed1c8476ce68eb7152dfcbc5330cefcbaa91"},{"url":"https://git.kernel.org/stable/c/b14a682ad7d45345701e08f9279d483a1da8b36c"},{"url":"https://git.kernel.org/stable/c/f5b143f4cd3fb7673df8d727550478a4b762908a"},{"url":"https://git.kernel.org/stable/c/2d06cb25a497d3a7034ef9d172626c2d6620a0f1"},{"url":"https://git.kernel.org/stable/c/8f27260b989f488760289276377db24fbfb20bfa"},{"url":"https://git.kernel.org/stable/c/8bc60db48e8cba35488bbd6e1f94aa990afa275a"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:41:14.790Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.18.58"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"7.2.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}