PT-2026-61230 · Linux · Linux
CVE-2026-63913
·
Published
2026-07-19
·
Updated
2026-07-19
CVSS v3.1
8.2
High
| Vector | AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H |
In the Linux kernel, the following vulnerability has been resolved:
netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check
An unintended behavior in the TCP conntrack state machine allows a
connection to be forced into the CLOSE state using an RST packet with an
invalid sequence number.
Specifically, after a SYN packet is observed, an RST with an invalid SEQ
can transition the conntrack entry to TCP CONNTRACK CLOSE, regardless of
whether the RST corresponds to the expected reply direction. The relevant
code path assumes the RST is a response to an outgoing SYN, but does not
validate packet direction or ensure that a matching SYN was actually sent
in the opposite direction.
As a result, a crafted packet sequence consisting of a SYN followed by an
invalid-sequence RST can prematurely terminate an active NAT entry. This
makes connection teardown easier than intended.
So, tighten the state transition logic to ensure that RST-triggered
CLOSE transitions only occur when the RST is a valid response to a
previously observed SYN in the correct direction.
Fix
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Related Identifiers
Affected Products
Linux