CVE-2026-63913

CVE Enrichment

CVSS: 8.2 HIGH
EPSS: 0.97%
EPSS Percentile: 61.70%
CISA KEV: Not listed

Description

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.

Technical Details

CVSS Version: 3.1
CNA / NVD Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published: 19-Jul-2026 23:17
Last Modified: 20-Oct-2026 04:17
EPSS Date: 2026-10-25
CWE: CWE-20

CVSS Vector


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

References

Last enrichment sync: 03-Nov-2026 05:07
Sources: NVD · FIRST EPSS · CISA KEV
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Reported Context (1)

Two CVEs have been assigned to date: CVE-2026-56181, affecting Microsoft Windows NAT in Hyper-V, and CVE-2026-63913, affecting the Linux netfilter conntrack subsystem. Black Hat USA 2026: Vendors Announce Security Products and Research

CVE (1)

People (1)

Vendors (14)

Products (19)

Industries (1)

Note: Related entities, including threat actors, malware, CVEs, MITRE ATT&CK techniques, vendors, products, tools, countries, and industries, are shown when they appear in the same reporting. Their presence does not necessarily mean they were targeted, compromised, vulnerable, responsible for the activity, or directly involved in the incident.