CVE-2026-34956 Openvswitch: open vswitch: denial of service via malformed ftp epasv command
Remote attackers can cause a denial of service in Open vSwitch by sending malformed FTP commands when FTP helpers are enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-34956?
CVE-2026-34956 is a medium-severity denial of service vulnerability in Red Hat Fast Datapath for RHEL 7, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-120
Which versions are affected by CVE-2026-34956?
Linux distribution packages (7)
openvswitch3 SUSE:Linux Enterprise Micro 5.5 | All versions | 3.1.7-150500.3.28.1 |
openvswitch SUSE:Linux Enterprise Module for Package Hub 15 SP7 | All versions | 3.5.4-150700.41.15.1 |
openvswitch SUSE:Linux Enterprise Module for Server Applications 15 SP7 | All versions | 3.5.4-150700.41.15.1 |
openvswitch SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | All versions | 2.11.5-3.30.1 |
openvswitch SUSE:Linux Micro 6.0 | All versions | 3.1.7-5.1 |
openvswitch SUSE:Linux Micro 6.1 | All versions | 3.1.7-slfo.1.1_3.1 |
openvswitch openSUSE:Tumbleweed | All versions | 3.7.1-33.1 |
How do I fix CVE-2026-34956?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-34956 being exploited?
There is no known exploitation of CVE-2026-34956 in the wild and no public exploit code.
Sources
Also known as AZL-86781, DEBIAN-CVE-2026-34956, GHSA-q5f5-xxh8-jx9h, OESA-2026-1871, OESA-2026-1872, OESA-2026-1960 and 10 more.