# 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.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 May 2026
- **Updated:** 1 Sep 2026
- **Also known as:** AZL-86781, DEBIAN-CVE-2026-34956, GHSA-q5f5-xxh8-jx9h, OESA-2026-1871, OESA-2026-1872, OESA-2026-1960, OESA-2026-1961, OESA-2026-1962, OESA-2026-2063, SUSE-SU-2026:1439-1, SUSE-SU-2026:1440-1, SUSE-SU-2026:1482-1, SUSE-SU-2026:21250-1, SUSE-SU-2026:22068-1, UBUNTU-CVE-2026-34956, openSUSE-SU-2026:10534-1

## 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 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2026-34956?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `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.

## Is CVE-2026-34956 being exploited?

There is no known exploitation of CVE-2026-34956 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34956 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-34956 in the wild and no public exploit code.

Affected product: Red Hat Fast Datapath for RHEL 7. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-34956/ (Markdown: https://insights.sbomify.com/CVE-2026-34956/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34956
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34956
- OSV: https://osv.dev/vulnerability/CVE-2026-34956

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34956/
Summaries are generated and may contain mistakes; the official description above is the record.