CVE-2024-52791 in matrix-media-repo
Summary
by MITRE • 01/16/2025
Matrix Media Repo (MMR) is a highly configurable multi-homeserver media repository for Matrix. MMR makes requests to other servers as part of normal operation, and these resource owners can return large amounts of JSON back to MMR for parsing. In parsing, MMR can consume large amounts of memory and exhaust available memory. This is fixed in MMR v1.3.8. Users are advised to upgrade. For users unable to upgrade; forward proxies can be configured to block requests to unsafe hosts. Alternatively, MMR processes can be configured with memory limits and auto-restart. Running multiple MMR processes concurrently can help ensure a restart does not overly impact users.
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Analysis
by VulDB Data Team • 08/20/2025
The Matrix Media Repo (MMR) vulnerability CVE-2024-52791 represents a critical memory exhaustion issue that affects the configuration of multi-homeserver media repositories within the Matrix communication protocol ecosystem. This vulnerability manifests when MMR performs requests to external servers as part of its normal operational workflow, creating a scenario where resource owners can return substantial JSON payloads that trigger excessive memory consumption within the MMR process. The flaw exists in the JSON parsing mechanism of the software, where the application fails to implement adequate memory limits or resource constraints during the processing of external data responses. The vulnerability is particularly concerning because it directly impacts the availability and stability of the media repository service, potentially leading to complete system outages or denial of service conditions that affect all users relying on the Matrix ecosystem for communication.
The technical exploitation of this vulnerability occurs through the normal operational flow of MMR when it interacts with remote servers to retrieve media content or metadata. When these external servers return large JSON responses, the MMR parsing routine consumes progressively more memory until system resources are exhausted, causing the application to crash or become unresponsive. This type of vulnerability falls under the CWE-400 category of "Uncontrolled Resource Consumption" and represents a classic example of a resource exhaustion attack that can be triggered by manipulating the size of incoming data responses. The vulnerability is classified as a memory leak or memory exhaustion issue that operates at the application layer, specifically affecting the JSON parsing and data processing components of the software. The attack vector is straightforward - an attacker can simply configure a malicious server to return large JSON responses that cause MMR to consume excessive memory resources.
The operational impact of CVE-2024-52791 extends beyond simple service disruption to potentially compromise the entire Matrix communication infrastructure that relies on the affected media repository. When memory exhaustion occurs, the MMR service becomes unavailable to legitimate users, disrupting media sharing capabilities across Matrix homeservers that depend on this repository. The vulnerability affects organizations and individuals who operate Matrix servers, particularly those managing large-scale communication platforms or federated networks where media content sharing is critical. The risk is amplified because the attack can be executed remotely without requiring authentication or specialized access, making it particularly dangerous in open network environments. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 "Endpoint Resource Exhaustion: Resource Exhaustion" and T1566.002 "Phishing: Spearphishing Attachment," as it can be exploited through malicious server responses or manipulated media content that triggers the vulnerable parsing behavior.
The remediation approach for CVE-2024-52791 involves multiple defensive strategies that organizations can implement to protect their Matrix infrastructure. The primary solution is upgrading to MMR version 1.3.8, which includes patches that address the memory consumption issues in JSON parsing operations. For environments where immediate upgrades are not feasible, several mitigation techniques can be employed. Network-level protections such as forward proxy configurations can be implemented to block requests to known unsafe hosts or to limit the size of responses that can be processed by MMR. Process-level controls including memory limits and automatic restart mechanisms provide additional layers of protection by ensuring that even if memory exhaustion occurs, the system can recover without complete service disruption. The recommended approach of running multiple MMR processes concurrently aligns with standard high availability practices and provides redundancy that prevents single points of failure in the media repository infrastructure. Organizations should also consider implementing monitoring solutions to detect unusual memory consumption patterns that could indicate exploitation attempts, and establish incident response procedures that include rapid deployment of patches or temporary workarounds when vulnerabilities are identified in operational systems.