---
cve: "CVE-2026-63913"
severity: "HIGH"
cvss: 8.2
epss: "62%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-07-19 16:17:09"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-11T00:43:04+02:00"
---

# CVE-2026-63913

> 8.2 HIGH

## Beschreibung

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.

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Gering | warn |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 5.10.259
- Kernel ≥ 5.15.210
- Kernel ≥ 6.1.176
- Kernel ≥ 6.6.143
- Kernel ≥ 6.12.93
- Kernel ≥ 6.18.35
- Kernel ≥ 7.0.12

## Referenzen

- <https://git.kernel.org/stable/c/2006979a15af5404bf932a325357683c0bac1656>
- <https://git.kernel.org/stable/c/6476c17d536dbd321c073242e762ddb2713a1238>
- <https://git.kernel.org/stable/c/f5547bebc416d56f56fb5b86dc20aabfa42165a0>
- <https://git.kernel.org/stable/c/2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77>
- <https://git.kernel.org/stable/c/f206def4e86d810f927ba1d8e322ea72b29bce58>
- <https://git.kernel.org/stable/c/b98ab51c45c5608a1c19ce7fd17a3032469bb83f>
- <https://git.kernel.org/stable/c/d67c6adee8d1b65330d0174c4c367faba14e80a8>
- <https://git.kernel.org/stable/c/bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-63913) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_