CVE-2002-0964
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 · uneditedHalf-Life Server 1.1.1.0 and earlier allows remote attackers to cause a denial of service (resource exhaustion) via multiple responses to the initial challenge with different cd_key values, which reaches the player limit and prevents other players from connecting until the original responses have timed out.
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 confidenceHalf-Life Server 1.1.1.0 and earlier contains a flaw in its CD key challenge-response authentication mechanism. Remote attackers can send multiple spoofed authentication responses with different cd_key values to the server's challenge, causing each fake response to consume a player slot. By exhausting all player slots through this method, attackers prevent legitimate players from connecting until the fraudulent connections time out, resulting in resource exhaustion and denial of service.
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= 1.1.0.4= 1.1.0.8= 1.1.0.9= 1.1.1.0<= 3.1= 3.1.3CVSS 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 Half-Life server versionRun 'hl_version' command if available, or check the server executable's properties/version info. On Linux/SSH, use 'strings hlds' or check the binary metadata for version string.Affected if Installed version matches 1.1.0.4, 1.1.0.9, 1.1.1.0 for Half-Life, or <= 3.1 / 3.1.3 for Half-Life Dedicated Server
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Verify CD key authentication is enabledCheck server configuration file (usually server.cfg or the command line startup parameters) for +set cd_key value or look for the absence of sv_lan 1 which forces CD key validation for internet play.Affected if CD key validation is enabled (sv_lan is 0 or not set) - this is the default behavior that enables the vulnerable authentication mechanism
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Monitor player slot consumptionUse the 'status' console command on the server or query the server via RCON to see current player count and maxplayers setting. Look for unusual numbers of connections or connections that do not show as fully connected players.Affected if Player count reaches maxplayers with many incomplete/phantom connections present, indicating slot exhaustion attack
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Check network logs for authentication anomaliesReview server logs for repeated authentication failures or unusual patterns in cd_key challenge-response activity. Look for many failed or spoofed authentication attempts from the same source.Affected if Logs show excessive authentication attempts or many invalid cd_key values being submitted
You are affected if you are running Half-Life Server 1.1.1.0 or earlier, or Half-Life Dedicated Server 3.1.3 or earlier, with CD key authentication enabled (default) and are experiencing slot exhaustion or seeing anomalous authentication patterns.
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 dataUpgrade to a patched version of the Half-Life server if available from the vendor. If no vendor patch exists, implement connection rate limiting and enforce stricter validation on challenge responses at the network level to mitigate abuse.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2002-0964 — 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-2002-0964 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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- 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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