iOSOperating system · Cisco
CVE-2003-0512
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 · uneditedCisco IOS 12.2 and earlier generates a "% Login invalid" message instead of prompting for a password when an invalid username is provided, which allows remote attackers to identify valid usernames on the system and conduct brute force password guessing, as reported for the Aironet Bridge.
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 confidenceIn Cisco IOS 12.2 and earlier, the login authentication process reveals different error messages depending on whether a username exists in the system. When an invalid username is entered, the system displays '% Login invalid' without prompting for a password, whereas a valid username would trigger a password prompt. This difference allows remote attackers to enumerate valid usernames and then conduct targeted brute force password attacks.
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
iOSOperating system
= 12.0\(24\)s1= 12.0\(24.2\)s= 12.2\(11\)ja1= 12.2\(14.5\)= 12.2\(14.5\)t= 12.2\(15\)zn= 12.2\(15.1\)s= 12.2\(16\)b= 12.2\(16.1\)bCVSS 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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Identify the Cisco IOS versionRun 'show version' on the device console or via remote access to display the IOS versionAffected if The displayed version matches one of the affected versions: 12.0(24)s1, 12.0(24.2)s, 12.2(11)ja1, 12.2(14.5), 12.2(14.5)t, 12.2(15)zn, 12.2(15.1)s, 12.2(16)b, or 12.2(16.1)b
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Check for local user accountsRun 'show running-config | include username' or view the configuration to see if local username entries are definedAffected if Local username entries exist in the configuration and the device uses local authentication
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Test login response with invalid usernameAttempt to log in via console, SSH, or telnet using a username that does not exist in the local database, observe whether you receive only '% Login invalid' without being prompted for a passwordAffected if The system returns '% Login invalid' immediately without prompting for a password, indicating the enumeration vulnerability is present
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Verify if AAA authentication is configuredRun 'show running-config | include aaa' or check if 'authentication login' is configured to use RADIUS or TACACS+Affected if AAA authentication with RADIUS or TACACS+ is NOT configured, meaning the device relies on local authentication which exhibits the vulnerable behavior
The environment is affected if the device runs an affected Cisco IOS version from the list and uses local authentication without AAA, allowing different error messages to reveal valid usernames.
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 Cisco IOS version beyond 12.2. Additionally, implement AAA authentication with RADIUS or TACACS+ servers and configure account lockout policies to mitigate brute force attempts.
Fix this in iOS
Scoped from the published advisory
- Consultation3.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2003-0512 — 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-2003-0512 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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- Version or environment caveats, and links to real fixes
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