Open vSwitch FTP Helper Heap OOB Leads to DoS
CVE-2026-34956 Published on May 5, 2026

Openvswitch: open vswitch: denial of service via malformed ftp epasv command
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.

NVD

Vulnerability Analysis

CVE-2026-34956 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
HIGH
Privileges Required:
NONE
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Timeline

Reported to Red Hat.

Made public.

Weakness Type

What is a Classic Buffer Overflow Vulnerability?

The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. A buffer overflow condition exists when a program attempts to put more data in a buffer than it can hold, or when a program attempts to put data in a memory area outside of the boundaries of a buffer. The simplest type of error, and the most common cause of buffer overflows, is the "classic" case in which the program copies the buffer without restricting how much is copied. Other variants exist, but the existence of a classic overflow strongly suggests that the programmer is not considering even the most basic of security protections.

CVE-2026-34956 has been classified to as a Classic Buffer Overflow vulnerability or weakness.


Products Associated with CVE-2026-34956

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Red Hat Enterprise Linux (RHEL)
 
Red Hat Openshift
 
Red Hat Openstack
 

Affected Versions

Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 7: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 8: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Fast Datapath for RHEL 9: Red Hat Enterprise Linux 7: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenShift Container Platform 4: Red Hat OpenStack Platform 13 (Queens): Red Hat OpenStack Platform 13 (Queens): Red Hat OpenStack Platform 13 (Queens): Red Hat OpenStack Platform 16.2: Red Hat OpenStack Platform 16.2: Red Hat OpenStack Platform 17.1: Red Hat OpenStack Platform 17.1: Red Hat OpenStack Platform 18.0: