CVE-2024-21655 in Discourse
Summary
by MITRE • 01/12/2024
Discourse is a platform for community discussion. For fields that are client editable, limits on sizes are not imposed. This allows a malicious actor to cause a Discourse instance to use excessive disk space and also often excessive bandwidth. The issue is patched 3.1.4 and 3.2.0.beta4.
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Analysis
by VulDB Data Team • 02/02/2024
The vulnerability CVE-2024-21655 represents a critical resource exhaustion flaw within the Discourse community discussion platform that affects versions prior to 3.1.4 and 3.2.0.beta4. This vulnerability stems from inadequate input validation mechanisms that govern client-editable fields within the platform's data handling architecture. The absence of size limitations on user-editable content creates a pathway for malicious actors to exploit the system's storage and bandwidth resources through carefully crafted submissions that exceed normal operational parameters.
The technical implementation of this vulnerability resides in the platform's failure to enforce proper data validation controls on fields that users can modify directly. When users submit content through editable fields, the system does not impose reasonable constraints on the maximum allowable size of these inputs. This design flaw allows attackers to submit arbitrarily large payloads that can consume substantial disk space and network bandwidth resources. The vulnerability manifests when malicious actors leverage this weakness to upload or modify content that grows exponentially beyond normal usage patterns, effectively creating a denial of service condition through resource exhaustion.
The operational impact of CVE-2024-21655 extends beyond simple resource consumption to encompass broader system stability and availability concerns. Attackers can systematically consume disk space by submitting large files or content that expands the database size beyond acceptable limits, potentially leading to complete system outages when storage capacity is exhausted. Additionally, the excessive bandwidth consumption affects network performance and can degrade service quality for legitimate users. This vulnerability directly impacts the platform's reliability and can result in significant operational costs related to storage expansion and bandwidth management.
Security practitioners should note that this vulnerability aligns with CWE-126, which addresses memory buffer over-read conditions, and reflects patterns commonly seen in input validation failures that enable resource exhaustion attacks. The ATT&CK framework categorizes this as a resource exhaustion technique under the broader category of denial of service attacks, where adversaries leverage system weaknesses to consume computational resources. Organizations should prioritize patching this vulnerability to prevent potential exploitation that could lead to service disruption and increased operational overhead.
The mitigation strategy for CVE-2024-21655 requires immediate deployment of patches version 3.1.4 or 3.2.0.beta4, which implement proper size limits for client-editable fields. System administrators should also consider implementing additional monitoring controls to detect unusual resource consumption patterns that might indicate exploitation attempts. Organizations running older versions should conduct thorough assessments of their Discourse installations and establish automated patch management processes to prevent similar vulnerabilities from emerging in the future. The fix addresses the root cause by enforcing maximum size constraints on all user-editable fields, thereby preventing the exploitation vector that enables excessive resource consumption.