tcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction
In the Linux kernel, the following vulnerability has been resolved: tcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction Blamed commit moved the TIME_WAIT-derived ISN from the skb control block to a per-CPU variable, assuming the value would always be consumed by tcp_conn_request() for the same packet that wrote it. That assumption is violated by multiple drop paths between the producer (__this_cpu_write(tcp_tw_isn, isn) in tcp_v{4,6}_rcv()) and the consumer (tcp_conn_request()): - min_ttl / min_hopcount check - xfrm policy check - tcp_inbound_hash() MD5/AO mismatch - tcp_filter() eBPF/SO_ATTACH_FILTER drop - th->syn && th->fin discard in tcp_rcv_state_process() TCP_LISTEN - psp_sk_rx_policy_check() in tcp_v{4,6}_do_rcv() - tcp_checksum_complete() in tcp_v{4,6}_do_rcv() - tcp_v{4,6}_cookie_check() returning NULL When a packet is dropped on any of these paths, tcp_tw_isn is left set. The next SYN processed on the same CPU then consumes the non zero value in tcp_conn_request(), receiving a potentially predictable ISN. This patch moves back tcp_tw_isn to skb->cb[], getting rid of the per-cpu variable. Note that tcp_v{4,6}_fill_cb() do not set it. Very litle impact on overall code size/complexity: $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new add/remove: 0/0 grow/shrink: 2/1 up/down: 8/-15 (-7) Function old new delta tcp_v6_rcv 3038 3042 +4 tcp_v4_rcv 3035 3039 +4 tcp_conn_request 2938 2923 -15 Total: Before=24436060, After=24436053, chg -0.00%
CVE-2026-64024
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-2026-64024
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": "41eecbd712b73f0d5dcf1152b9a1c27b1f238028",
"lessThan": "8bb6aa419b142dcc2680177ecc39c4c38db7fc16",
"versionType": "git"
},
{
"status": "affected",
"version": "41eecbd712b73f0d5dcf1152b9a1c27b1f238028",
"lessThan": "e47f7060eaf60894e3e4d0e3c4fe6e1f2eacfbdd",
"versionType": "git"
},
{
"status": "affected",
"version": "41eecbd712b73f0d5dcf1152b9a1c27b1f238028",
"lessThan": "4affe063fa56c880cbea8d0bfded0bb80751579d",
"versionType": "git"
},
{
"status": "affected",
"version": "41eecbd712b73f0d5dcf1152b9a1c27b1f238028",
"lessThan": "1bbf0ced1d9db73ac7893c2187f3459288603e0d",
"versionType": "git"
}
],
"programFiles": [
"include/net/tcp.h",
"net/ipv4/tcp.c",
"net/ipv4/tcp_input.c",
"net/ipv4/tcp_ipv4.c",
"net/ipv6/tcp_ipv6.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.10"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.10",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.114",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.34",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.0.11",
"versionType": "semver",
"lessThanOrEqual": "7.0.*"
},
{
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"include/net/tcp.h",
"net/ipv4/tcp.c",
"net/ipv4/tcp_input.c",
"net/ipv4/tcp_ipv4.c",
"net/ipv6/tcp_ipv6.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-64024
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #46414 · Revision 1
- Added to Heist Feed
- Publisher date