---
id: CVE-2026-34956
title: A flaw was found in Open vSwitch
summary: >-
  A flaw was found in Open vSwitch. When Open vSwitch is configured with a
  conntrack flow using FTP helpers over the userspace datapath, a remote
  attacker can send a specially crafted FTP stream with an EPASV command
  exceeding 255 characte…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-120
published: '2026-05-05'
updated: '2026-08-21'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34956'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-34956'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2453459'
    label: secalert@redhat.com
  - url: 'http://www.openwall.com/lists/oss-security/2026/03/31/15'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00635
epssPercentile: 0.48234
ingestedAt: '2026-08-22T01:24:51.197Z'
---

## Overview

A flaw was found in Open vSwitch. When Open vSwitch is configured with a conntrack flow using FTP helpers over the userspace datapath, a remote attacker can send a specially crafted FTP stream with an EPASV command exceeding 255 characters. This heap access error can lead to a crash, resulting in a Denial of Service (DoS) for the affected system.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.