NVD / CVE Program· CNA redhat

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

Noroxi assessment

Priority: Monitor (action score 23/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.40% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
Fixed version: azl3 openvswitch 3.3.0-2 on Azure Linux 3.0 3.3.0-3; azl3 openvswitch 3.3.0-3 on Azure Linux 3.0 3.3.0-3.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to azl3 openvswitch 3.3.0-2 on Azure Linux 3.0 3.3.0-3; azl3 openvswitch 3.3.0-3 on Azure Linux 3.0 3.3.0-3 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.9 · v3.1—No exploit Fix available

Published: May 5, 2026
Updated: Nov 5, 2026
EPSS: 0.4% · 35th percentile
CWE: CWE-120

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 23 / 40 · 5.9 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · redhat: 5.9; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

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

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	openvswitch	from 0	—
Debian:14	openvswitch	before 3.7.1-1	3.7.1-1
openSUSE:Leap 16.0	openvswitch	before 3.5.4-160000.4.1	3.5.4-160000.4.1
openSUSE:Tumbleweed	openvswitch	before 3.7.1-33.1	3.7.1-33.1
SUSE:Linux Enterprise Micro 5.5	openvswitch3	before 3.1.7-150500.3.28.1	3.1.7-150500.3.28.1
SUSE:Linux Enterprise Module for Package Hub 15 SP7	openvswitch	before 3.5.4-150700.41.15.1	3.5.4-150700.41.15.1
SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5	openvswitch	before 2.11.5-3.30.1	2.11.5-3.30.1
SUSE:Linux Micro 6.0	openvswitch	before 3.1.7-5.1	3.1.7-5.1
SUSE:Linux Micro 6.1	openvswitch	before 3.1.7-slfo.1.1_3.1	3.1.7-slfo.1.1_3.1
SUSE:Linux Micro 6.2	openvswitch	before 3.5.4-160000.4.1	3.5.4-160000.4.1

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
azl3 openvswitch 3.3.0-2 on Azure Linux 3.0	3.3.0-3 · CBL-Mariner Releases	Microsoft (MSRC)
azl3 openvswitch 3.3.0-3 on Azure Linux 3.0	3.3.0-3 · CBL-Mariner Releases	Microsoft (MSRC)
debian:openvswitch	3.7.1-1 · Debian:14	Package registry (OSV)
opensuse:openvswitch	3.7.1-33.1 · openSUSE:Tumbleweed	Package registry (OSV)
suse:openvswitch	3.5.4-150700.41.15.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7	Package registry (OSV)
suse:openvswitch3	3.1.7-150500.3.28.1 · SUSE:Linux Enterprise Micro 5.5	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Seiji Sakurai

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-26-0177 · May 6, 2026(Open vSwitch Güvenlik Güncellemesi)

All national notices →

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
Special conditions such as timing or configuration are required.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Root cause

When data is copied, the source length is not compared with the size of the destination buffer. Excess data overwrites adjacent memory.

The bug in code

The whole CWE-120 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1char buf[256];
2memcpy(buf, pkt->data, pkt->len);

Fixed

1char buf[256];
2if (pkt->len > sizeof(buf)) {
3  return -EINVAL;
4}
5memcpy(buf, pkt->data, pkt->len);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

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Change log

Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

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References

access.redhat.com/security/cve/CVE-2026-34956

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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