Source: cve@mitre.org
Plone 4.1.3 and earlier computes hash values for form parameters without restricting the ability to trigger hash collisions predictably, which allows remote attackers to cause a denial of service (CPU consumption) by sending many crafted parameters.
Plone CMS versions 4.1.3 and earlier are vulnerable to a denial-of-service (DoS) attack due to a flaw in how they handle form parameter hashing. Attackers can exploit this vulnerability by sending a large number of specially crafted form parameters, causing excessive CPU consumption on the server. This can lead to significant service disruption and potential data loss.
Step 1: Payload Preparation: The attacker crafts a large number of form parameters. These parameters are designed to trigger hash collisions within the Plone CMS's form processing logic. The attacker carefully selects parameter values that, when hashed, will result in the same hash value. Step 2: Payload Delivery: The attacker sends the crafted form parameters to the vulnerable Plone CMS instance. This is typically done via an HTTP POST request, targeting a form submission endpoint. Step 3: Hash Collision Trigger: The Plone CMS receives the form parameters and begins processing them. The vulnerable hashing algorithm is used to compute hash values for each parameter. Due to the crafted parameters, many of these parameters will result in hash collisions. Step 4: CPU Exhaustion: The Plone CMS, encountering numerous hash collisions, spends a significant amount of CPU time comparing the colliding parameters. This leads to a rapid increase in CPU usage, potentially reaching 100%. Step 5: Denial of Service: The excessive CPU consumption starves other processes, leading to a denial of service. Legitimate users are unable to access the Plone CMS, and the server may become unresponsive or crash.
The vulnerability stems from a weakness in Plone's handling of form parameter hashing. Specifically, the software uses a hashing algorithm that is susceptible to hash collisions. An attacker can craft a large number of form parameters that, when hashed, collide with each other. This forces the server to repeatedly compare these colliding values, leading to a significant increase in CPU usage. The root cause is the lack of proper collision resistance in the hashing algorithm used for form parameter processing. This allows for the creation of a hash collision attack, where an attacker can deliberately cause the hash function to produce the same hash value for different inputs, leading to a performance degradation.
While no specific APTs are directly linked to this CVE, the ease of exploitation makes it a potential target for various threat actors. This type of DoS attack is often used as a precursor to other attacks or as a distraction. Not listed on CISA KEV.
Monitor server CPU usage for sudden and sustained spikes, especially during periods of high traffic.
Analyze web server logs for suspicious POST requests containing a large number of parameters.
Implement intrusion detection system (IDS) rules to identify requests with a high number of parameters or specific parameter patterns known to trigger hash collisions.
Monitor network traffic for unusual patterns of POST requests to Plone CMS instances.
Examine server resource utilization (CPU, memory, disk I/O) for signs of exhaustion.
Upgrade to Plone version 4.1.4 or later, which includes a fix for this vulnerability.
Implement a web application firewall (WAF) to filter malicious requests. Configure the WAF to limit the number of parameters allowed in a single request.
Rate-limit requests from individual IP addresses to prevent abuse.
Monitor server logs and network traffic for suspicious activity.
Regularly update and patch all software components, including the operating system and any third-party libraries used by Plone.