CVE-2012-5496: Denial of Service in Kupu in Plone
Summary
CVE-2012-5496: kupu_spellcheck.py in Kupu in Plone before 4.0 allows remote attackers to cause a denial of service (ZServer thread lock) via a crafted URL. Affects plone versions < 3.3.6. Fixed in 3.3.6. How to fix ↓
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Background
Plone is an open-source content management system built on top of the Zope application server. It provides a user-friendly interface for managing websites and supports various features such as content editing, versioning, and workflow management. Kupu is a rich-text editor used in Plone for creating and editing content. It includes a spell-checking feature that can be accessed via a URL.
Vulnerability Detail
The vulnerability (CVE-2012-5496) exists in the 'kupu_spellcheck.py' module of Kupu in Plone versions prior to 4.0. An attacker can exploit this vulnerability by sending a specially crafted URL to the server. When the server processes the URL, it triggers a denial of service condition by causing a ZServer thread lock. This can result in the unavailability of the affected Plone instance, impacting its functionality and accessibility.
How To Fix
Latest published version: 6.2.2 as of 23 Oct 2026
pip install --upgrade "plone==6.2.2"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
3.3.6
This is the first release that contains the fix.
pip install --upgrade "plone==3.3.6"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
No workaround has been provided for this vulnerability.
Conclusion
In conclusion, the CVE-2012-5496 vulnerability in Kupu in Plone versions prior to 4.0 allows remote attackers to cause a denial of service by exploiting a thread lock issue. To mitigate this vulnerability, it is advised to upgrade Plone to version 3.3.6 or later. For further assistance or support in vulnerability remediation, please contact DevNack.com.
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FAQ
The vulnerability can lead to a denial of service condition, causing the affected Plone instance to become unresponsive and inaccessible.
You can use the Vulert Playground at Vulert Scanner to check if your Plone instance is affected by this vulnerability. Simply enter your Pipfile.lock and it will provide real-time alerts for open-source vulnerabilities.
There are no known public exploits available for this vulnerability at the time of this report.
Yes, a patch is available in Plone version 3.3.6 and later. It is recommended to upgrade to the latest version to mitigate the vulnerability.
Yes, this vulnerability can be exploited remotely by sending a specially crafted URL to the server.
References
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