CVE-2011-1757
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 · uneditedDJabberd 0.84 and earlier does not properly detect recursion during entity expansion, which allows remote attackers to cause a denial of service (memory and CPU consumption) via a crafted XML document containing a large number of nested entity references, a similar issue to CVE-2003-1564.
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 confidenceDJabberd 0.84 and earlier fails to limit or detect recursive XML entity expansion during parsing. An attacker can send a crafted XML document with deeply nested entity references (billion laughs attack variant), causing the server to consume excessive memory and CPU while expanding the entities repeatedly until resources are exhausted.
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<= 0.84= 0.80= 0.81= 0.82= 0.83CVSS 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 if DJabberd is installedLocate DJabberd binaries, libraries, or the running process on the system. Common locations include /usr/bin/djabberd, /usr/local/bin/djabberd, or check running processes for 'djabberd'.Affected if DJabberd is found running or installed on the system
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Determine installed DJabberd versionRun 'djabberd --version' or check the version string in the installed package/libraries. Common commands: 'dpkg -l | grep djabberd', 'rpm -qa | grep djabberd', or inspect the Perl module version if installed via CPAN.Affected if The installed version is 0.80, 0.81, 0.82, 0.83, or 0.84 (any version <= 0.84)
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Verify XML parsing is enabled for XMPP connectionsInspect DJabberd configuration files (typically djabberd.conf or similar) for XML parsing settings related to XMPP stanza processing. Check if the XML parser is actively used for incoming connections.Affected if XML parsing is enabled and processing incoming XMPP stanzas
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Check for entity expansion limits in XML parserExamine the XML parser configuration or Perl XML parser settings used by DJabberd. Look for options like XML::LibXML, XML::Parser, or similar Perl XML modules and check if any limits are set on entity expansion, nesting depth, or memory usage.Affected if No entity expansion limits, nesting depth limits, or parsing timeouts are configured for the XML parser
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Check if the server accepts external XMPP connectionsVerify that the DJabberd service is exposed to network connections (listening on external interfaces, not just localhost). Review firewall rules and bind address settings in the configuration.Affected if The server accepts external or untrusted XMPP connections
A user is affected if DJabberd version 0.84 or earlier is installed with XML parsing enabled for incoming connections and no entity expansion limits configured in the XML parser.
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 DJabberd that implements entity expansion limits, or configure the XML parser to restrict or disable entity expansion. Consider implementing XML parsing timeouts and memory limits as defense-in-depth.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2011-1757 — 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-2011-1757 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
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