Denial of Service in Wagtail CMS via Rendition Processing

Executive Summary

This vulnerability exists in Wagtail, an open source content management system built on Django. In versions prior to 7.0.8, 7.3.3, and 7.4.2, an authenticated admin user can trigger expensive rendition processing by using purposefully crafted filter specifications. This can lead to potential service degradation.

It is important to note that this vulnerability cannot be exploited by ordinary site visitors without access to the Wagtail admin interface.

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Detection Guidance

This vulnerability can be detected by monitoring for unusually high resource consumption related to image rendition processing triggered by authenticated admin users in affected Wagtail versions prior to 7.0.8, 7.3.3, and 7.4.2.

Since the issue involves expensive image processing triggered by crafted filter specifications, detection involves observing performance degradation or high CPU/memory usage on the Wagtail server during admin operations.

There are no specific commands provided in the resources to detect this vulnerability directly. However, general system monitoring commands can help identify symptoms of exploitation, such as:

• Using top or htop to monitor CPU and memory usage: `top` or `htop`
• Checking for high load averages: `uptime` or `cat /proc/loadavg`
• Monitoring web server logs for unusual admin activity or repeated image rendition requests
• Using network monitoring tools like tcpdump or Wireshark to analyze traffic patterns from authenticated admin sessions

For a more precise detection, reviewing the Wagtail application logs for errors or slow responses during image processing may help identify exploitation attempts.

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Impact Analysis

The vulnerability can cause service degradation by allowing an authenticated admin user to trigger resource-intensive rendition processing. This may slow down or disrupt the normal operation of the Wagtail content management system.

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Compliance Impact

This vulnerability allows an authenticated admin user to trigger expensive rendition processing that may lead to service degradation. However, it does not involve unauthorized access to sensitive data or compromise confidentiality or integrity.

Since the vulnerability does not expose personal data or affect data integrity, it is unlikely to directly impact compliance with standards such as GDPR or HIPAA, which focus on protecting personal and health information.

Nevertheless, service degradation could affect availability, which is a component of these regulations, but only if it results in significant downtime or denial of service impacting users' access to protected data.

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Mitigation Strategies

To mitigate this vulnerability, upgrade Wagtail to one of the fixed versions: 7.0.8, 7.3.3, or 7.4.2.

Since the vulnerability requires authenticated admin access, restrict admin user access and monitor for unusual rendition processing activity to reduce risk until the upgrade is applied.

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