{"id":"CVE-2026-64007","title":"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…","summary":"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…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-416"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 3.12, < 5.10.259","linux_kernel >= 5.11, < 5.15.210","linux_kernel >= 5.16, < 6.1.176","linux_kernel >= 6.2, < 6.6.143","linux_kernel >= 6.7, < 6.12.93","linux_kernel >= 6.13, < 6.18.35","linux_kernel >= 6.19, < 7.0.12","linux_kernel = 7.1"],"patched":["linux_kernel 7.0.12"],"published":"2026-07-19","updated":"2026-10-13","sourceUpdated":"2026-10-13T14:05:42.053","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64007","references":[{"url":"https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9902a1058992de5d95656b64a3bd95c077f7ba2c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a91887a5b6ee4b98dfbf1db657ed2b879430149e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/af2c22ccb1f621aff487ff47a040e38e058541e7","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c7f945f7da097245a2f8ed7775ce48421047ee96","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d3019c61799adc21811af4b521f11f3dc77f8e04","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dd206819f210522579010d889d45a9530bb494bc","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00514,"epssPercentile":0.42182,"ingestedAt":"2026-10-13T14:29:01.773Z","slug":"CVE-2026-64007","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `linux_kernel >= 3.12, < 5.10.259`\n- `linux_kernel >= 5.11, < 5.15.210`\n- `linux_kernel >= 5.16, < 6.1.176`\n- `linux_kernel >= 6.2, < 6.6.143`\n- `linux_kernel >= 6.7, < 6.12.93`\n- `linux_kernel >= 6.13, < 6.18.35`\n- `linux_kernel >= 6.19, < 7.0.12`\n- `linux_kernel = 7.1`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 7.0.12`","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}