CVE-2021-33509: Plone Remote Authenticated Managers Disk I/O Vulnerability
Summary
CVE-2021-33509: Plone through 5.2.4 allows remote authenticated managers to perform disk I/O via crafted keyword arguments to the ReStructuredText transform in a Python script. Affects plone versions < 5.2.5. Fixed in 5.2.5. 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 creation, collaboration, and workflow management. Plone is widely used in both small and large organizations to create and maintain their web presence. However, a vulnerability has been discovered in Plone versions up to 5.2.4 that allows remote authenticated managers to perform disk I/O operations through crafted keyword arguments to the ReStructuredText transform in a Python script.
Vulnerability Detail
The vulnerability in Plone allows authenticated managers to abuse the ReStructuredText transform in a Python script to perform disk I/O operations. By providing specially crafted keyword arguments, an attacker can manipulate the script to read or write files on the server's filesystem. This can lead to unauthorized access to sensitive information, modification of critical files, or even a complete compromise of the server. The vulnerability requires authentication as a manager, which limits the potential attackers to authorized users with elevated privileges.
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
5.2.5
This is the first release that contains the fix.
pip install --upgrade "plone==5.2.5"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If upgrading to the latest version of Plone is not immediately feasible, a temporary workaround can be implemented by restricting access to the ReStructuredText transform in Python scripts. This can be achieved by modifying the access control settings or disabling the transform altogether. However, this workaround may impact the functionality of certain features or scripts that rely on the transform, so it is recommended to apply the official fix as soon as possible.
Conclusion
Plone versions up to 5.2.4 are vulnerable to a remote authenticated managers disk I/O vulnerability. This can allow attackers with elevated privileges to perform unauthorized disk I/O operations, potentially leading to unauthorized access or modification of critical files. It is recommended to upgrade to Plone version 5.2.5 or later to fix the vulnerability. If immediate upgrade is not possible, applying the temporary workaround of restricting access to the ReStructuredText transform can provide some protection. For further support on vulnerability remediation, please contact DevNack.com.
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FAQ
Plone versions up to 5.2.4 are affected by this vulnerability. If you are using an older version of Plone, it is recommended to upgrade to the latest version to ensure the security of your system.
An attacker with authenticated manager privileges can abuse this vulnerability to perform unauthorized disk I/O operations. This can lead to unauthorized access to sensitive information, modification of critical files, or even a complete compromise of the server.
Yes, authentication as a manager is required to exploit this vulnerability. Regular users or anonymous visitors do not have the necessary privileges to perform the malicious disk I/O operations.
There are no known instances of this vulnerability being exploited in the wild at the time of this report. However, it is important to apply the necessary patches or upgrades to mitigate the risk.
The recommended course of action is to upgrade to Plone version 5.2.5 or later. This ensures that the vulnerability is patched and the system is secure. If immediate upgrade is not possible, applying the temporary workaround of restricting access to the ReStructuredText transform can provide some protection.
References
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