{"id":"CVE-2026-64007","revision":"fcc19b307ad249aa9e0ae62ed47552b9","records":[{"revision":"fcc19b307ad249aa9e0ae62ed47552b9","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-64007","aliases":[],"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":0,"publishedAt":"2026-07-19T14:56:23.049+00:00","modifiedAt":"2026-10-19T20:28:08.086+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/netfilter/nf_synproxy_core.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"9902a1058992de5d95656b64a3bd95c077f7ba2c\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"d3019c61799adc21811af4b521f11f3dc77f8e04\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"dd206819f210522579010d889d45a9530bb494bc\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"af2c22ccb1f621aff487ff47a040e38e058541e7\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"c7f945f7da097245a2f8ed7775ce48421047ee96\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"f0fea2b6d5453a11ad11713bbf37561b9b3a7edf\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"a91887a5b6ee4b98dfbf1db657ed2b879430149e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"48b1de4c110a7afa4b85862f6c75af817db26fad\",\n                            \"lessThan\": \"92170e6afe927ab2792a3f71902845789c8e31b1\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/netfilter/nf_synproxy_core.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"3.12\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"3.12\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.259\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.210\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.176\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.143\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.93\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.35\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.0.12\",\n                            \"lessThanOrEqual\": \"7.0.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/9902a1058992de5d95656b64a3bd95c077f7ba2c","https://git.kernel.org/stable/c/d3019c61799adc21811af4b521f11f3dc77f8e04","https://git.kernel.org/stable/c/dd206819f210522579010d889d45a9530bb494bc","https://git.kernel.org/stable/c/af2c22ccb1f621aff487ff47a040e38e058541e7","https://git.kernel.org/stable/c/c7f945f7da097245a2f8ed7775ce48421047ee96","https://git.kernel.org/stable/c/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf","https://git.kernel.org/stable/c/a91887a5b6ee4b98dfbf1db657ed2b879430149e","https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64007","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-64007","identifiers":["CVE-2026-64007"]},"retained":false,"historicalAffected":[]}],"coverage":[]}