CVE-2006-6421
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 · uneditedCross-site scripting (XSS) vulnerability in the private message box implementation (privmsg.php) in phpBB 2.0.x allows remote authenticated users to inject arbitrary web script or HTML via the "Message body" field in a message to a non-existent user.
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 confidenceCross-site scripting (XSS) vulnerability in phpBB 2.0.x's private messaging system (privmsg.php) allows authenticated remote users to inject arbitrary JavaScript or HTML through the message body field when attempting to send a message to a non-existent user. The unsanitized input is reflected back in the response, enabling script execution in the context of other users viewing the message.
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= 2.0= 2.0.0= 2.0.1= 2.0.2= 2.0.3= 2.0.4= 2.0.5= 2.0.6= 2.0.6c= 2.0.6d= 2.0.7= 2.0.7aCVSS 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
- M
- Authentication
- Single
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:M/Au:S/C:P/I:P/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 phpBB versionCheck the version.php file or database configuration for the installed phpBB version numberAffected if The installed version is 2.0.x (specifically 2.0 through 2.0.7a)
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Locate privmsg.phpFind the privmsg.php file in the phpBB installation directory (typically in the root or /includes/ folder depending on phpBB structure)Affected if The file exists and belongs to the phpBB 2.0.x installation
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Inspect message body handling in privmsg.phpExamine the source code of privmsg.php for how the message body field is processed when sending a message to a non-existent user. Look for whether htmlspecialchars or equivalent output encoding is applied to user-supplied message content before it is reflected in the response.Affected if The message body input is reflected back without htmlspecialchars or ENT_QUOTES encoding, or no sanitization is found for the error message displaying the attempted recipient
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Verify private messaging is enabledCheck the phpBB admin panel or configuration to confirm the private messaging feature (user -> private messaging) is enabled for at least some usersAffected if Private messaging functionality is active, allowing the vulnerable code path to be triggered
You are affected if phpBB 2.0.x version 2.0 through 2.0.7a is installed, privmsg.php exists, and the message body field is not sanitized with htmlspecialchars before being reflected in the error response when attempting to message a non-existent user.
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 dataApply output encoding (htmlspecialchars with ENT_QUOTES) to the message body field in privmsg.php before display, or upgrade to a patched version of phpBB that addresses this XSS vulnerability.
- Consultation2.0 h
- Implementation3.0 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-2006-6421 — 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-2006-6421 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
- No spam, self-promotion, credentials, or personal data