SECUFOCUSNOW
Home›CVE index›CVE-2026-63913
Review reviewHigh

CVE-2026-63913

Linux

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...

CVSS
8.2
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.20
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 8.2

Vulnerability overview

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...

Affected product and versions

Product
Linux
Affected versions
>= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < 2006979a15af5404bf932a325357683c0bac1656, >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < 6476c17d536dbd321c073242e762ddb2713a1238, >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < f5547bebc416d56f56fb5b86dc20aabfa42165a0, >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < 2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77, >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < f206def4e86d810f927ba1d8e322ea72b29bce58, >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < b98ab51c45c5608a1c19ce7fd17a3032469bb83f, >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < d67c6adee8d1b65330d0174c4c367faba14e80a8, >= 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 < bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a, >= 2.6.15
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
CWE
Not available