CVE-2026-15711
Summary
by MITRE • 07/14/2026
A vulnerability was found in libsoup's WebSocket frame parsing implementation. The library fails to validate length rules specified in RFC 6455 §5.5, which mandates that all WebSocket control frames (e.g., PING, PONG, CLOSE) contain a payload of 125 bytes or less. A remote, unauthenticated attacker can exploit this by sending a non-compliant, oversized control frame. Because the parser handles this protocol violation improperly instead of throwing an immediate connection termination error, it triggers a internal processing crash, resulting in a remote denial of service (DoS) for applications utilizing libsoup WebSockets.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability resides within libsoup's WebSocket implementation where the library fails to properly validate WebSocket frame lengths according to RFC 6455 section 5.5 specifications. This critical flaw affects the parsing logic that handles WebSocket control frames including PING, PONG, and CLOSE messages which must contain payloads no larger than 125 bytes. The absence of proper validation creates an exploitable condition where malicious actors can craft oversized control frames that violate these fundamental protocol requirements.
The technical implementation error manifests when the WebSocket parser encounters a control frame exceeding the 125-byte limit specified in RFC 6455. Rather than immediately terminating the connection upon detecting this protocol violation, the parser continues processing and eventually crashes during internal frame handling operations. This improper error handling stems from inadequate input validation at the protocol layer, creating a path for remote code execution through controlled memory corruption that leads to application instability.
From an operational perspective, this vulnerability presents a severe denial of service risk for any applications relying on libsoup's WebSocket functionality. The remote unauthenticated nature of the exploit means attackers can trigger the DoS condition without requiring prior access credentials or privileges. Applications utilizing libsoup for real-time communication, web-based services, or any WebSocket-dependent infrastructure become immediately vulnerable to disruption attacks that can render services unavailable to legitimate users.
The vulnerability maps directly to CWE-129 and CWE-787 within the Common Weakness Enumeration framework, representing issues related to insufficient input validation and out-of-bounds writes respectively. From an ATT&CK methodology perspective, this represents a denial of service attack technique (T1499) that leverages protocol implementation flaws to compromise system availability. The attack vector requires only network access to the target application, making it particularly dangerous in environments where WebSocket services are exposed to untrusted networks.
Mitigation strategies should prioritize immediate patching of affected libsoup versions to implement proper RFC 6455 compliance enforcement. Organizations should also consider implementing network-level firewalls or proxy configurations that can filter oversized WebSocket frames before they reach vulnerable applications. Additionally, application-level monitoring and alerting systems should be deployed to detect unusual WebSocket traffic patterns that may indicate exploitation attempts. Regular security assessments of WebSocket implementations and proactive protocol compliance verification will help prevent similar vulnerabilities from emerging in future deployments.