CVE-2023-43826Public exploitNetwork attack vector

Code execution via undersized VNC frame buffer

Published Dec 19, 2023 · Updated Feb 25, 2026

Integer overflow in VNC frame-buffer handling in Apache Guacamole 1.5.3 and earlier allows remote attackers to execute code via crafted updates. In guac_vnc_update, h multiplied by the Cairo stride can wrap before allocation, while nested loops still copy the full image into the undersized heap buffer. The attacker must control or compromise a VNC server that a Guacamole user connects to; successful exploitation runs code with guacd privileges.

CVSS severity7.5
High
EPSS probability0.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in VNC frame-buffer handling in Apache Guacamole 1.5.3 and earlier allows remote attackers to execute code via crafted updates. In guac_vnc_update, h multiplied by the Cairo stride can wrap before allocation, while nested loops still copy the full image into the undersized heap buffer. The attacker must control or compromise a VNC server that a Guacamole user connects to; successful exploitation runs code with guacd privileges.

The record

CVE
CVE-2023-43826
Published
Dec 19, 2023
Updated
Feb 25, 2026
Vendor
The Apache Software Foundation
Product
Apache Guacamole
Classifications
CWE-190, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 19, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=1.5.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Apache Software Foundation · Apache Guacamoleversion=0 <=1.5.3

Published CVSS scores

0.0Apache Software FoundationCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:N
7.5Apache Software FoundationCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.0Apache Software FoundationCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1203Exploitation for Client Execution

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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