CVE-2025-27458
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 · uneditedThe VNC authentication mechanism bases on a challenge-response system where both server and client use the same password for encryption. The challenge is sent from the server to the client, is encrypted by the client and sent back. The server does the same encryption locally and if the responses match it is prooven that the client knows the correct password. Since all VNC communication is unencrypted, an attacker can obtain the challenge and response and try to derive the password from this information.
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 confidenceVNC's challenge-response authentication transmits the challenge and encrypted response in plaintext across the network. An attacker can intercept these values and perform offline password cracking to recover the authentication password.
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 dataall versionsCVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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 checksWork through these to decide whether this CVE applies to you.
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Identify if VNC service is runningCheck for listening VNC ports (typically 5900-5910) using 'netstat -tuln | grep -E "590[0-9]"' or 'ss -tuln | grep -E "590[0-9]"'Affected if VNC ports are open and listening on network interfaces
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Verify VNC authentication typeCheck VNC server configuration for authentication method: review /etc/vnc/config or similar config files, or query the VNC server directly to confirm it uses VNC authentication (DES/3DES challenge-response) rather than external authenticationAffected if VNC is configured to use standard challenge-response authentication without encryption wrapper
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Confirm no SSH tunnel is in use for VNCCheck running processes for SSH port forwarding (grep for ssh -L or ssh -R with VNC ports) and verify no VPN tunnel is active for VNC trafficAffected if VNC traffic flows directly over network without SSH tunnel or VPN encapsulation
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Test network exposure of VNCCapture network traffic on the VNC port using tcpdump or Wireshark to observe if challenge and encrypted response are transmitted in plaintextAffected if Network capture shows unencrypted challenge-response packets on VNC port
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Verify encryption wrapper is not deployedReview firewall rules, network configuration, and any port forwarding rules to confirm VNC port is not behind an encrypted tunnel or VPNAffected if VNC port 5900+ is directly accessible from network without encryption layer
You are affected if VNC service is running with unencrypted challenge-response authentication exposed directly to the network without SSH tunnel or VPN protection.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor dataWrap VNC connections in encrypted tunnels using SSH port forwarding or VPN, or deploy VNC servers with stronger authentication mechanisms and encrypted transport.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-27458 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-27458 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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
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