CVE-2026-63913High· 8.2▾ TwilightIn 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 …
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 45.1 · likelihood 0.2 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.
Exploit-prediction probability, daily snapshots since Oct 16.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CVEORG
1.0%
Last analysed / modified upstream
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.
Linux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < 2006979a15af5404bf932a325357683c0bac1656Linux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < 6476c17d536dbd321c073242e762ddb2713a1238Linux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < f5547bebc416d56f56fb5b86dc20aabfa42165a0Linux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < 2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77Linux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < f206def4e86d810f927ba1d8e322ea72b29bce58Linux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < b98ab51c45c5608a1c19ce7fd17a3032469bb83fLinux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < d67c6adee8d1b65330d0174c4c367faba14e80a8Linux >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9aLinux 2.6.15Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Connected by shared product, vendor, weakness, or advisory.
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