TomcatWeb server / proxy · Apache
CVE-2012-2733
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 · uneditedjava/org/apache/coyote/http11/InternalNioInputBuffer.java in the HTTP NIO connector in Apache Tomcat 6.x before 6.0.36 and 7.x before 7.0.28 does not properly restrict the request-header size, which allows remote attackers to cause a denial of service (memory consumption) via a large amount of header data.
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 HTTP NIO connector in Apache Tomcat 6.x before 6.0.36 and 7.x before 7.0.28 fails to properly restrict request-header size, allowing remote attackers to send arbitrarily large amounts of header data that exhausts server memory and causes 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
TomcatWeb server / proxy
= 6.0= 6.0.0= 6.0.1= 6.0.2= 6.0.3= 6.0.4= 6.0.5= 6.0.6= 6.0.7= 6.0.8= 6.0.9= 6.0.10CVSS 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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Confirm Tomcat is runningIdentify Java processes running Tomcat: check for 'catalina' or 'tomcat' in process list, or look for the $CATALINA_HOME environment variable and the presence of Tomcat directories.Affected if Tomcat is not in use, this CVE does not apply.
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Identify installed Tomcat versionRun the version.sh script in the Tomcat bin directory, or inspect the manifest of catalina.jar in the lib folder to read the Implementation-Version attribute.Affected if Version is 6.0.x before 6.0.36, or 7.0.x before 7.0.28.
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Determine if HTTP NIO connector is in useExamine the server.xml configuration file (typically in $CATALINA_HOME/conf/) and look for a <Connector> element with the protocol attribute set to org.apache.coyote.http11.Http11NioProtocol or a similar NIO implementation.Affected if The NIO connector is configured and the Tomcat version falls within the affected range.
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Check for header size limitsIn the same server.xml file, inspect any <Connector> definitions for the maxHeaderSize attribute. Look for a configured value that limits header buffer size.Affected if No maxHeaderSize is set on the NIO connector, leaving the default unlimited header processing in place.
You are affected if Tomcat is running with the HTTP NIO connector and the installed version is 6.0.x before 6.0.36 or 7.0.x before 7.0.28 with no maxHeaderSize limit configured.
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 Tomcat 6.0.36+ or 7.0.28+ which implements proper header size limits. Additionally, configure maxHeaderSize limits as a defense-in-depth measure.
Fix this in Tomcat
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 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 $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2012-2733 — 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-2012-2733 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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