CVE-2026-34956Public exploitNetwork attack vector

Service crash via FTP length truncation

Published May 5, 2026 · Updated May 5, 2026

Heap overflow in Open vSwitch 2.8.0 through 3.7.0 allows remote attackers to crash the service via crafted FTP traffic. The conntrack replace_substring function narrows packet and substring lengths from size_t to uint8_t, so a 256-byte size becomes zero and drives an oversized memmove. Triggering requires the userspace datapath and an explicitly configured conntrack flow with the FTP ALG; handlers are disabled by default.

CVSS severity5.9
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap overflow in Open vSwitch 2.8.0 through 3.7.0 allows remote attackers to crash the service via crafted FTP traffic. The conntrack replace_substring function narrows packet and substring lengths from size_t to uint8_t, so a 256-byte size becomes zero and drives an oversized memmove. Triggering requires the userspace datapath and an explicitly configured conntrack flow with the FTP ALG; handlers are disabled by default.

The record

CVE
CVE-2026-34956
Published
May 5, 2026
Updated
May 5, 2026
Vendor
389 Directory Server
Product
Red Hat Enterprise Linux 7
Classifications
CWE-120, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 5, 2026CVE publishedPublication date reported by the CVE source.
  2. May 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · Red Hat Enterprise Linux 7Affected versions are unavailable in this record.
389 Directory Server · Red Hat OpenStack PlatformAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux Fast DatapathAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenStack Services on OpenShiftAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift Container PlatformAffected versions are unavailable in this record.

Published CVSS scores

5.9Red Hat, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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