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GuacamoleApplication · Apache

CVE-2023-43826

HIGH · 8.8 CVSS v3.1 Published 2023-12-19
Fix available
A fix is available. Upgrade to after 1.5.3 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Apache Guacamole 1.5.3 and older do not consistently ensure that values received from a VNC server will not result in integer overflow. If a user connects to a malicious or compromised VNC server, specially-crafted data could result in memory corruption, possibly allowing arbitrary code to be executed with the privileges of the running guacd process. Users are recommended to upgrade to version 1.5.4, which fixes this issue.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Apache Guacamole versions 1.5.3 and older fail to properly validate values received from VNC servers, leading to integer overflow vulnerabilities. When a user connects to a malicious or compromised VNC server, specially-crafted data can cause memory corruption, potentially allowing arbitrary code execution with the privileges of the guacd process.

MitigationUpgrade Apache Guacamole to version 1.5.4 or later. Until upgraded, avoid connecting to untrusted VNC servers.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
GuacamoleApplication
Affected:<= 1.5.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Apache Guacamole version
    Check the installed version of guacd (the Guacamole daemon) using 'guacd --version' or check the package version via your system package manager (dpkg, rpm, yum, etc.). If using the web client, also check the deployed Guacamole web application version.
    Affected if The installed version is 1.5.3 or any version lower than 1.5.3 (e.g., 1.5.2, 1.5.1, 1.5.0, 1.4.x, etc.).
  2. Verify VNC protocol support is present
    Check if the Guacamole installation includes VNC protocol support. This is typically provided by the guacd daemon and associated client libraries. Look for VNC-related configuration files or logs indicating VNC connection attempts.
    Affected if VNC protocol support is compiled into or loaded by the guacd daemon, or VNC connections have been configured in Guacamole.
  3. Review active VNC connections or configurations
    Examine Guacamole connection configurations (usually stored in database or configuration files) for any defined VNC connections. Check logs for recent VNC activity.
    Affected if There are defined VNC connections or recent VNC connection history through this Guacamole instance.

You are affected if your Apache Guacamole installation is version 1.5.3 or older AND you have VNC protocol support enabled or have configured VNC connections.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 1.5.3
Interim mitigation

Upgrade Apache Guacamole to version 1.5.4 or later. Until upgraded, avoid connecting to untrusted VNC servers.

Recommended fix High confidence

1.5.4

  1. 1. Identify the current Guacamole version running in your environment
  2. 2. Backup all Guacamole configuration files, user settings, and any custom configurations
  3. 3. Download Apache Guacamole version 1.5.4 from the official Apache repository (https://guacamole.apache.org/releases/)
  4. 4. Upgrade the guacd daemon to version 1.5.4
  5. 5. Upgrade the Guacamole web application (guacamole.war) to version 1.5.4 if using the all-in-one package
  6. 6. Restart the guacd service to apply the changes
  7. 7. Verify the upgrade was successful by checking the version number in the Guacamole UI or via command line
  8. 8. Test VNC connections to ensure functionality is intact
Caveat Review release notes for 1.5.4 to check for any configuration or feature changes that may affect your deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Guacamole Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-43826 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data