CVE-2024-52815 in synapse
Summary
by MITRE • 12/03/2024
Synapse is an open-source Matrix homeserver. Synapse versions before 1.120.1 fail to properly validate invites received over federation. This vulnerability allows a malicious server to send a specially crafted invite that disrupts the invited user's /sync functionality. Synapse 1.120.1 rejects such invalid invites received over federation and restores the ability to sync for affected users.
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Analysis
by VulDB Data Team • 08/26/2025
The vulnerability identified as CVE-2024-52815 affects Synapse, an open-source Matrix homeserver implementation that serves as the backbone for decentralized messaging infrastructure. This security flaw resides in the federation protocol handling mechanism where the software fails to properly validate incoming invitation requests from other Matrix servers. The issue specifically impacts versions prior to 1.120.1, creating a persistent security gap that malicious actors could exploit to disrupt legitimate user communication channels. The Matrix protocol relies heavily on federated servers to maintain network connectivity and user experience, making this vulnerability particularly concerning for organizations dependent on secure messaging infrastructure.
The technical implementation flaw stems from inadequate input validation within the federation invite processing pipeline. When a malicious server sends a crafted invite message, the vulnerable Synapse versions do not properly sanitize or verify the invitation parameters before processing them. This validation failure creates a condition where malformed or maliciously constructed invite requests can bypass normal security checks and corrupt the internal state of the affected server. The vulnerability manifests in the user's synchronization process, which is fundamental to maintaining real-time communication state and message delivery. According to CWE standards, this represents a weakness in input validation and improper error handling that allows for disruption of service through malformed data processing.
The operational impact of CVE-2024-52815 extends beyond simple service disruption to potentially compromise user experience and communication integrity across the federated Matrix network. Affected users experience complete breakdown in their /sync functionality, preventing them from receiving new messages, seeing read receipts, or maintaining proper chat state synchronization. This disruption affects the core functionality that Matrix users rely upon for real-time communication, effectively rendering their accounts partially or fully non-functional within the federated ecosystem. From an ATT&CK framework perspective, this vulnerability maps to technique T1499.004 (Network Denial of Service) and T1566.002 (Phishing via Service) as it can be leveraged to disrupt services while potentially serving as a vector for more sophisticated attacks targeting user accounts and communication channels.
The remediation implemented in Synapse version 1.120.1 addresses this vulnerability through enhanced validation mechanisms that reject malformed invites at the federation level. This update introduces stricter input validation procedures that verify invite parameters against established Matrix protocol specifications before accepting and processing any federation invitation requests. The fix ensures that only properly formatted and legitimate invitations are processed, preventing maliciously crafted requests from corrupting the internal state of the server. Organizations running older Synapse versions should prioritize immediate upgrade to 1.120.1 or later to mitigate this risk, as the vulnerability remains exploitable in unpatched installations. The fix aligns with security best practices outlined in NIST SP 800-34 and ISO/IEC 27001 standards for maintaining secure communication infrastructure and preventing service disruption attacks.