CVE-2005-1133
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 POP3 server in IBM iSeries AS/400 returns different error messages when the user exists or not, which allows remote attackers to determine valid user IDs on the server.
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 confidenceThe POP3 server in IBM iSeries AS/400 returns distinct error messages for valid versus invalid usernames during authentication. This differential response allows remote attackers to enumerate valid user accounts on the system through repeated connection attempts.
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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- None
- Availability
- None
AV:N/AC:L/Au:N/C:P/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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Confirm POP3 server is enabled on the systemAccess IBM iSeries AS/400 system management (WRKSRVTSE or similar) and verify the POP3 server service (usually service name 'POP3' or port 110) is started and listeningAffected if POP3 server is actively running and accepting connections on port 110
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Identify POP3 service configurationUse system commands (such as WRKTCPSTS or NETSTAT) to confirm the POP3 daemon is bound to port 110 and accessible from networkAffected if POP3 service is bound to a reachable network interface
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Test authentication response for non-existent userConnect to the POP3 server (telnet <server> 110) and issue USER command with a clearly invalid username (e.g., USER nonexistentuser123), then observe the error responseAffected if Server returns an error message indicating the user does not exist (e.g., '-ERR User unknown' or similar)
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Test authentication response for valid userConnect to the POP3 server and issue USER command with a known valid username (e.g., USER admin or USER existingaccount), then observe the error responseAffected if Server returns a different error message for valid users versus invalid ones, or returns a response suggesting the user exists (e.g., '+OK User valid' or similar)
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Compare error message behaviorPerform multiple authentication attempts with various usernames (both real and fabricated) and document whether the server provides distinguishable responses that reveal account validityAffected if Error messages differ between valid and invalid usernames, enabling enumeration
A user is affected if the POP3 server is running and returns distinct error messages that reveal whether a given username is valid on the system.
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 dataConfigure the POP3 server to return identical error messages (e.g., 'Authentication failed') regardless of whether the username exists, preventing user enumeration. Consider implementing rate limiting or account lockout policies as additional defense-in-depth measures.
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2005-1133 — 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-2005-1133 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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