netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63913
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:09 UTC
Updated2026-07-20 15:16:55 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 8.2 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

EPSS: 0.002270000 probability, percentile 0.134990000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
3.1CNADECLARED8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 2006979a15af5404bf932a325357683c0bac1656 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 6476c17d536dbd321c073242e762ddb2713a1238 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 f5547bebc416d56f56fb5b86dc20aabfa42165a0 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 f206def4e86d810f927ba1d8e322ea72b29bce58 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 b98ab51c45c5608a1c19ce7fd17a3032469bb83f git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 d67c6adee8d1b65330d0174c4c367faba14e80a8 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a git Not specified
CNA Linux Linux affected 2.6.15 Not specified
CNA Linux Linux unaffected 2.6.15 semver Not specified
CNA Linux Linux unaffected 5.10.259 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/2006979a15af5404bf932a325357683c0bac1656 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d67c6adee8d1b65330d0174c4c367faba14e80a8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f5547bebc416d56f56fb5b86dc20aabfa42165a0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f206def4e86d810f927ba1d8e322ea72b29bce58 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b98ab51c45c5608a1c19ce7fd17a3032469bb83f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6476c17d536dbd321c073242e762ddb2713a1238 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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