{"api_version":"1","generated_at":"2026-05-03T12:43:37+00:00","cve":"CVE-2026-43037","urls":{"html":"https://cve.report/CVE-2026-43037","api":"https://cve.report/api/cve/CVE-2026-43037.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-43037","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-43037"},"summary":{"title":"ip6_tunnel: clear skb2->cb[] in ip4ip6_err()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6_tunnel: clear skb2->cb[] in ip4ip6_err()\n\nOskar Kjos reported the following problem.\n\nip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written\nby the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes\nIPCB(skb2) to __ip_options_echo(), which interprets that cb[] region\nas struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff\nat offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr\nvalue. __ip_options_echo() then reads optlen from attacker-controlled\npacket data at sptr[rr+1] and copies that many bytes into dopt->__data,\na fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE).\n\nTo fix this we clear skb2->cb[], as suggested by Oskar Kjos.\n\nAlso add minimal IPv4 header validation (version == 4, ihl >= 5).","state":"PUBLISHED","assigner":"Linux","published_at":"2026-05-01 15:16:48","updated_at":"2026-05-03 07:16:23"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"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","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/2edfa31769a4add828a7e604b21cb82aaaa05925","name":"https://git.kernel.org/stable/c/2edfa31769a4add828a7e604b21cb82aaaa05925","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/1063515ce15ff31065c4e7f8265f4c2fd3c54876","name":"https://git.kernel.org/stable/c/1063515ce15ff31065c4e7f8265f4c2fd3c54876","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a0c4ce9900a108eaf55d0f3b399cb55999647d39","name":"https://git.kernel.org/stable/c/a0c4ce9900a108eaf55d0f3b399cb55999647d39","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d6621f60192fe10c047a4487be42a6f4c150707f","name":"https://git.kernel.org/stable/c/d6621f60192fe10c047a4487be42a6f4c150707f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3","name":"https://git.kernel.org/stable/c/590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ea9f65b27c8404e164848ebff1443310fd187629","name":"https://git.kernel.org/stable/c/ea9f65b27c8404e164848ebff1443310fd187629","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5","name":"https://git.kernel.org/stable/c/2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4a622658f384b03560834cbe8ffcfe69a278f7c8","name":"https://git.kernel.org/stable/c/4a622658f384b03560834cbe8ffcfe69a278f7c8","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-43037","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43037","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c4d3efafcc933fd2ffd169d7dc4f980393a13796 ea9f65b27c8404e164848ebff1443310fd187629 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c4d3efafcc933fd2ffd169d7dc4f980393a13796 d6621f60192fe10c047a4487be42a6f4c150707f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c4d3efafcc933fd2ffd169d7dc4f980393a13796 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c4d3efafcc933fd2ffd169d7dc4f980393a13796 a0c4ce9900a108eaf55d0f3b399cb55999647d39 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"43037","cve":"CVE-2026-43037","epss":"0.000240000","percentile":"0.068220000","score_date":"2026-05-02","updated_at":"2026-05-03 00:00:23"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/ipv6/ip6_tunnel.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"ea9f65b27c8404e164848ebff1443310fd187629","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"},{"lessThan":"d6621f60192fe10c047a4487be42a6f4c150707f","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"},{"lessThan":"2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"},{"lessThan":"a0c4ce9900a108eaf55d0f3b399cb55999647d39","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"},{"lessThan":"1063515ce15ff31065c4e7f8265f4c2fd3c54876","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"},{"lessThan":"590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"},{"lessThan":"4a622658f384b03560834cbe8ffcfe69a278f7c8","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"},{"lessThan":"2edfa31769a4add828a7e604b21cb82aaaa05925","status":"affected","version":"c4d3efafcc933fd2ffd169d7dc4f980393a13796","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/ipv6/ip6_tunnel.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"2.6.22"},{"lessThan":"2.6.22","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.253","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.203","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.168","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.134","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.81","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.22","versionType":"semver"},{"lessThanOrEqual":"6.19.*","status":"unaffected","version":"6.19.12","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.0","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.253","versionStartIncluding":"2.6.22","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.203","versionStartIncluding":"2.6.22","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.168","versionStartIncluding":"2.6.22","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.134","versionStartIncluding":"2.6.22","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.81","versionStartIncluding":"2.6.22","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.22","versionStartIncluding":"2.6.22","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.19.12","versionStartIncluding":"2.6.22","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0","versionStartIncluding":"2.6.22","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6_tunnel: clear skb2->cb[] in ip4ip6_err()\n\nOskar Kjos reported the following problem.\n\nip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written\nby the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes\nIPCB(skb2) to __ip_options_echo(), which interprets that cb[] region\nas struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff\nat offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr\nvalue. __ip_options_echo() then reads optlen from attacker-controlled\npacket data at sptr[rr+1] and copies that many bytes into dopt->__data,\na fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE).\n\nTo fix this we clear skb2->cb[], as suggested by Oskar Kjos.\n\nAlso add minimal IPv4 header validation (version == 4, ihl >= 5)."}],"metrics":[{"cvssV3_1":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-05-03T05:46:16.322Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/ea9f65b27c8404e164848ebff1443310fd187629"},{"url":"https://git.kernel.org/stable/c/d6621f60192fe10c047a4487be42a6f4c150707f"},{"url":"https://git.kernel.org/stable/c/2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5"},{"url":"https://git.kernel.org/stable/c/a0c4ce9900a108eaf55d0f3b399cb55999647d39"},{"url":"https://git.kernel.org/stable/c/1063515ce15ff31065c4e7f8265f4c2fd3c54876"},{"url":"https://git.kernel.org/stable/c/590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3"},{"url":"https://git.kernel.org/stable/c/4a622658f384b03560834cbe8ffcfe69a278f7c8"},{"url":"https://git.kernel.org/stable/c/2edfa31769a4add828a7e604b21cb82aaaa05925"}],"title":"ip6_tunnel: clear skb2->cb[] in ip4ip6_err()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-43037","datePublished":"2026-05-01T14:15:35.314Z","dateReserved":"2026-05-01T14:12:55.978Z","dateUpdated":"2026-05-03T05:46:16.322Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-05-01 15:16:48","lastModifiedDate":"2026-05-03 07:16:23","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"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","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"43037","Ordinal":"1","Title":"ip6_tunnel: clear skb2->cb[] in ip4ip6_err()","CVE":"CVE-2026-43037","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"43037","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6_tunnel: clear skb2->cb[] in ip4ip6_err()\n\nOskar Kjos reported the following problem.\n\nip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written\nby the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes\nIPCB(skb2) to __ip_options_echo(), which interprets that cb[] region\nas struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff\nat offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr\nvalue. __ip_options_echo() then reads optlen from attacker-controlled\npacket data at sptr[rr+1] and copies that many bytes into dopt->__data,\na fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE).\n\nTo fix this we clear skb2->cb[], as suggested by Oskar Kjos.\n\nAlso add minimal IPv4 header validation (version == 4, ihl >= 5).","Type":"Description","Title":"ip6_tunnel: clear skb2->cb[] in ip4ip6_err()"}]}}}