netfilter: synproxy: refresh tcphdr after skb_ensure_writable
In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: refresh tcphdr after skb_ensure_writable synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer. Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale: caller (ipv[46]_synproxy_hook) th = skb_header_pointer(skb, ..., &_tcph) synproxy_tstamp_adjust(skb, protoff, th, ...) skb_ensure_writable(skb, optend) pskb_expand_head() /* kfree(old skb->head) */ ... inet_proto_csum_replace4(&th->check, ...) /* writes into freed head, or into the caller's stack copy leaving the on-wire checksum stale */ The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload. Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable heade
CVE-2026-64007
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-64007
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "9902a1058992de5d95656b64a3bd95c077f7ba2c",
"versionType": "git"
},
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "d3019c61799adc21811af4b521f11f3dc77f8e04",
"versionType": "git"
},
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "dd206819f210522579010d889d45a9530bb494bc",
"versionType": "git"
},
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "af2c22ccb1f621aff487ff47a040e38e058541e7",
"versionType": "git"
},
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "c7f945f7da097245a2f8ed7775ce48421047ee96",
"versionType": "git"
},
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "f0fea2b6d5453a11ad11713bbf37561b9b3a7edf",
"versionType": "git"
},
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "a91887a5b6ee4b98dfbf1db657ed2b879430149e",
"versionType": "git"
},
{
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"lessThan": "92170e6afe927ab2792a3f71902845789c8e31b1",
"versionType": "git"
}
],
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "3.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "3.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.259",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.210",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.176",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.143",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.93",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.35",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.0.12",
"versionType": "semver",
"lessThanOrEqual": "7.0.*"
},
{
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-64007
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #40931 · Revision 1
- Added to Heist Feed
- Publisher date