CVE-2018-10657 in Synapse
Summary
by MITRE
Matrix Synapse before 0.28.1 is prone to a denial of service flaw where malicious events injected with depth = 2^63 - 1 render rooms unusable, related to federation/federation_base.py and handlers/message.py, as exploited in the wild in April 2018.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/05/2024
The vulnerability identified as CVE-2018-10657 represents a critical denial of service flaw affecting Matrix Synapse versions prior to 0.28.1. This vulnerability specifically targets the federation and message handling components of the Matrix protocol implementation, creating a scenario where malicious actors can render entire chat rooms unusable through carefully crafted events. The flaw exploits a fundamental weakness in how the system processes event depths, particularly when events are injected with an extremely large depth value of 2^63 - 1, which represents the maximum value for a signed 64-bit integer.
The technical implementation of this vulnerability resides in the federation/federation_base.py and handlers/message.py modules of the Matrix Synapse codebase. When a malicious event with depth set to 2^63 - 1 is processed, the system encounters a critical failure in its depth validation logic. This particular depth value triggers an integer overflow condition that causes the message processing pipeline to hang or crash, effectively preventing legitimate users from participating in the room. The flaw demonstrates a classic case of inadequate input validation and boundary condition handling within the federated messaging system, where the software fails to properly sanitize or reject malformed event data that could cause system instability.
The operational impact of this vulnerability extends beyond simple service disruption as it affects the fundamental integrity of Matrix federated networks. When exploited, malicious actors can create rooms that become permanently unusable, forcing administrators to either delete the problematic room or implement manual workarounds. The vulnerability was actively exploited in April 2018, indicating that it was not merely a theoretical concern but a real threat that compromised the availability of Matrix services across multiple implementations. This attack vector specifically targets the federation protocol, meaning that compromised rooms could affect the broader Matrix network as other servers attempt to synchronize with the malicious room.
The vulnerability aligns with CWE-191, Integer Underflow (Wrap or Wraparound), and CWE-190, Integer Overflow or Wraparound, as it involves the manipulation of integer values beyond their normal operational range. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, Network Denial of Service, and T1566.002, Prephishing, as it requires the injection of malicious events into the network. The exploitability of this vulnerability demonstrates how a single malformed event can cascade through the federated network, affecting multiple servers and users simultaneously. The lack of proper integer bounds checking in the event depth processing creates a scenario where the system cannot distinguish between legitimate and malicious depth values, making it particularly dangerous for distributed systems that rely on trust within the federation.
Mitigation strategies for this vulnerability include immediate patching to version 0.28.1 or later, which implements proper depth validation and integer boundary checks. Administrators should also implement monitoring for unusual depth values in incoming events and consider implementing rate limiting on event processing to prevent rapid exploitation. The fix addresses the root cause by ensuring that event depths are properly validated against reasonable bounds, preventing the overflow condition that leads to system instability. Additionally, network administrators should consider implementing automated detection mechanisms that can identify and quarantine rooms exhibiting suspicious depth patterns, providing an additional layer of defense against similar future attacks.