{"api_version":"1","generated_at":"2026-07-23T11:24:30+00:00","cve":"CVE-2026-64007","urls":{"html":"https://cve.report/CVE-2026-64007","api":"https://cve.report/api/cve/CVE-2026-64007.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-64007","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-64007"},"summary":{"title":"netfilter: synproxy: refresh tcphdr after skb_ensure_writable","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: refresh tcphdr after skb_ensure_writable\n\nsynproxy_tstamp_adjust() rewrites the TCP timestamp option in place\nand then patches the TCP checksum via inet_proto_csum_replace4() on\nthe caller-supplied tcphdr pointer.  Both ipv4_synproxy_hook() and\nipv6_synproxy_hook() obtain that pointer with skb_header_pointer()\nbefore calling in, so it may either alias skb->head directly or\npoint at the caller's on-stack _tcph buffer.\n\nBetween obtaining the pointer and using it, the function calls\nskb_ensure_writable(skb, optend), which on a cloned or non-linear\nskb invokes pskb_expand_head() and frees the old skb->head.  After\nthat point the cached th is stale:\n\n    caller (ipv[46]_synproxy_hook)\n      th = skb_header_pointer(skb, ..., &_tcph)\n      synproxy_tstamp_adjust(skb, protoff, th, ...)\n        skb_ensure_writable(skb, optend)\n          pskb_expand_head()        /* kfree(old skb->head) */\n        ...\n        inet_proto_csum_replace4(&th->check, ...)\n                                    /* writes into freed head, or\n                                       into the caller's stack copy\n                                       leaving the on-wire checksum\n                                       stale */\n\nThe option bytes are written through skb->data and are fine; only\nthe checksum update goes through th and so lands in the wrong\nplace.  The result is either a write into freed slab memory or a\npacket leaving with a checksum that does not match its payload.\n\nFix by re-deriving th from skb->data + protoff immediately after\nskb_ensure_writable() succeeds, so the subsequent checksum update\ntargets the linear, writable header.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 16:17:40","updated_at":"2026-07-20 15:17:01"},"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/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf","name":"https://git.kernel.org/stable/c/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/af2c22ccb1f621aff487ff47a040e38e058541e7","name":"https://git.kernel.org/stable/c/af2c22ccb1f621aff487ff47a040e38e058541e7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a91887a5b6ee4b98dfbf1db657ed2b879430149e","name":"https://git.kernel.org/stable/c/a91887a5b6ee4b98dfbf1db657ed2b879430149e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d3019c61799adc21811af4b521f11f3dc77f8e04","name":"https://git.kernel.org/stable/c/d3019c61799adc21811af4b521f11f3dc77f8e04","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/dd206819f210522579010d889d45a9530bb494bc","name":"https://git.kernel.org/stable/c/dd206819f210522579010d889d45a9530bb494bc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c7f945f7da097245a2f8ed7775ce48421047ee96","name":"https://git.kernel.org/stable/c/c7f945f7da097245a2f8ed7775ce48421047ee96","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1","name":"https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/9902a1058992de5d95656b64a3bd95c077f7ba2c","name":"https://git.kernel.org/stable/c/9902a1058992de5d95656b64a3bd95c077f7ba2c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-64007","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64007","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad 9902a1058992de5d95656b64a3bd95c077f7ba2c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad d3019c61799adc21811af4b521f11f3dc77f8e04 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad dd206819f210522579010d889d45a9530bb494bc git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad af2c22ccb1f621aff487ff47a040e38e058541e7 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad c7f945f7da097245a2f8ed7775ce48421047ee96 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad f0fea2b6d5453a11ad11713bbf37561b9b3a7edf git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad a91887a5b6ee4b98dfbf1db657ed2b879430149e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 48b1de4c110a7afa4b85862f6c75af817db26fad 92170e6afe927ab2792a3f71902845789c8e31b1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.12","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.12 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.10.259 5.10.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.210 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.176 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.143 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.93 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.35 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.12 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"64007","cve":"CVE-2026-64007","epss":"0.001760000","percentile":"0.073890000","score_date":"2026-07-20","updated_at":"2026-07-21 00:13:13"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/netfilter/nf_synproxy_core.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"9902a1058992de5d95656b64a3bd95c077f7ba2c","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"},{"lessThan":"d3019c61799adc21811af4b521f11f3dc77f8e04","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"},{"lessThan":"dd206819f210522579010d889d45a9530bb494bc","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"},{"lessThan":"af2c22ccb1f621aff487ff47a040e38e058541e7","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"},{"lessThan":"c7f945f7da097245a2f8ed7775ce48421047ee96","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"},{"lessThan":"f0fea2b6d5453a11ad11713bbf37561b9b3a7edf","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"},{"lessThan":"a91887a5b6ee4b98dfbf1db657ed2b879430149e","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"},{"lessThan":"92170e6afe927ab2792a3f71902845789c8e31b1","status":"affected","version":"48b1de4c110a7afa4b85862f6c75af817db26fad","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/netfilter/nf_synproxy_core.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"3.12"},{"lessThan":"3.12","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.259","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.210","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.176","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.143","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.93","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.35","versionType":"semver"},{"lessThanOrEqual":"7.0.*","status":"unaffected","version":"7.0.12","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.259","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.210","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.176","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.143","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.93","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.35","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0.12","versionStartIncluding":"3.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1","versionStartIncluding":"3.12","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: refresh tcphdr after skb_ensure_writable\n\nsynproxy_tstamp_adjust() rewrites the TCP timestamp option in place\nand then patches the TCP checksum via inet_proto_csum_replace4() on\nthe caller-supplied tcphdr pointer.  Both ipv4_synproxy_hook() and\nipv6_synproxy_hook() obtain that pointer with skb_header_pointer()\nbefore calling in, so it may either alias skb->head directly or\npoint at the caller's on-stack _tcph buffer.\n\nBetween obtaining the pointer and using it, the function calls\nskb_ensure_writable(skb, optend), which on a cloned or non-linear\nskb invokes pskb_expand_head() and frees the old skb->head.  After\nthat point the cached th is stale:\n\n    caller (ipv[46]_synproxy_hook)\n      th = skb_header_pointer(skb, ..., &_tcph)\n      synproxy_tstamp_adjust(skb, protoff, th, ...)\n        skb_ensure_writable(skb, optend)\n          pskb_expand_head()        /* kfree(old skb->head) */\n        ...\n        inet_proto_csum_replace4(&th->check, ...)\n                                    /* writes into freed head, or\n                                       into the caller's stack copy\n                                       leaving the on-wire checksum\n                                       stale */\n\nThe option bytes are written through skb->data and are fine; only\nthe checksum update goes through th and so lands in the wrong\nplace.  The result is either a write into freed slab memory or a\npacket leaving with a checksum that does not match its payload.\n\nFix by re-deriving th from skb->data + protoff immediately after\nskb_ensure_writable() succeeds, so the subsequent checksum update\ntargets the linear, writable header."}],"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":"2026-07-20T13:42:17.862Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/9902a1058992de5d95656b64a3bd95c077f7ba2c"},{"url":"https://git.kernel.org/stable/c/d3019c61799adc21811af4b521f11f3dc77f8e04"},{"url":"https://git.kernel.org/stable/c/dd206819f210522579010d889d45a9530bb494bc"},{"url":"https://git.kernel.org/stable/c/af2c22ccb1f621aff487ff47a040e38e058541e7"},{"url":"https://git.kernel.org/stable/c/c7f945f7da097245a2f8ed7775ce48421047ee96"},{"url":"https://git.kernel.org/stable/c/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf"},{"url":"https://git.kernel.org/stable/c/a91887a5b6ee4b98dfbf1db657ed2b879430149e"},{"url":"https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1"}],"title":"netfilter: synproxy: refresh tcphdr after skb_ensure_writable","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-64007","datePublished":"2026-07-19T14:56:23.049Z","dateReserved":"2026-07-19T07:54:57.026Z","dateUpdated":"2026-07-20T13:42:17.862Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 16:17:40","lastModifiedDate":"2026-07-20 15:17:01","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":"64007","Ordinal":"1","Title":"netfilter: synproxy: refresh tcphdr after skb_ensure_writable","CVE":"CVE-2026-64007","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"64007","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: refresh tcphdr after skb_ensure_writable\n\nsynproxy_tstamp_adjust() rewrites the TCP timestamp option in place\nand then patches the TCP checksum via inet_proto_csum_replace4() on\nthe caller-supplied tcphdr pointer.  Both ipv4_synproxy_hook() and\nipv6_synproxy_hook() obtain that pointer with skb_header_pointer()\nbefore calling in, so it may either alias skb->head directly or\npoint at the caller's on-stack _tcph buffer.\n\nBetween obtaining the pointer and using it, the function calls\nskb_ensure_writable(skb, optend), which on a cloned or non-linear\nskb invokes pskb_expand_head() and frees the old skb->head.  After\nthat point the cached th is stale:\n\n    caller (ipv[46]_synproxy_hook)\n      th = skb_header_pointer(skb, ..., &_tcph)\n      synproxy_tstamp_adjust(skb, protoff, th, ...)\n        skb_ensure_writable(skb, optend)\n          pskb_expand_head()        /* kfree(old skb->head) */\n        ...\n        inet_proto_csum_replace4(&th->check, ...)\n                                    /* writes into freed head, or\n                                       into the caller's stack copy\n                                       leaving the on-wire checksum\n                                       stale */\n\nThe option bytes are written through skb->data and are fine; only\nthe checksum update goes through th and so lands in the wrong\nplace.  The result is either a write into freed slab memory or a\npacket leaving with a checksum that does not match its payload.\n\nFix by re-deriving th from skb->data + protoff immediately after\nskb_ensure_writable() succeeds, so the subsequent checksum update\ntargets the linear, writable header.","Type":"Description","Title":"netfilter: synproxy: refresh tcphdr after skb_ensure_writable"}]}}}