# CVE-2026-34956: Openvswitch: open vswitch: denial of service via malformed ftp epasv command

CVE-2026-34956 is fixed in openvswitch on 1 platform, first by SUSE-SU-2026:1439-1, released April 17, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-34956
- Priority: Routine
- CVSS: 5.9 (Moderate)
- EPSS: 0.0041
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 17, 2026
- Weakness: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34956

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | openvswitch Debian 14 | 3.7.1-1 | [DEBIAN-CVE-2026-34956](https://patchblox.com/security/data/fix/linux/debian-cve-2026-34956.md) | May 15, 2026 |
| Linux | openvswitch opensuse-leap 16.0 | 3.5.4-160000.4.1 | [OPENSUSE-SU-2026:20972-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20972-1.md) | Jun 17, 2026 |
| Linux | openvswitch sles 15.7 | 3.5.4-150700.41.15.1 | [SUSE-SU-2026:1439-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-1439-1.md) | Apr 17, 2026 |
| Linux | openvswitch sles 16.0 | 3.5.4-160000.4.1 | [SUSE-SU-2026:22152-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22152-1.md) | Jun 17, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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