CVE-2026-102556 in Red Hat
Summary
by MITRE • 09/29/2026
A flaw was found in libsoup. When handling an incoming WebSocket Pong frame, SoupWebsocketConnection emitted the ::pong signal with a GByteArray pointer even though the signal is declared to pass a GBytes. Applications connecting a handler that follows the documented GBytes API can trigger heap corruption or a crash upon receiving a crafted Pong.
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability identified in libsoup represents a critical type mismatch within its WebSocket implementation, specifically affecting how incoming control frames are processed and signaled to application developers. The core of this issue lies in the SoupWebsocketConnection class, which is responsible for managing WebSocket connections and handling various frame types including text, binary, ping, and pong messages. When an incoming Pong frame arrives from a remote peer, the library is designed to emit a ::pong signal to notify any registered handlers about the event. However, there is a fundamental discrepancy between the actual data structure passed during this emission and the interface contract defined in the API documentation.
Technically, the flaw manifests as a type confusion error where the internal implementation passes a GByteArray pointer instead of the documented GBytes object when emitting the ::pong signal. This deviation from the specified Application Programming Interface means that applications which strictly adhere to the official documentation will expect a GBytes structure. When these applications attempt to interact with the passed data using methods appropriate for GBytes, they may inadvertently interpret memory structures incorrectly or access invalid pointers if the underlying implementation details are not aligned with their expectations. This mismatch creates an opportunity for heap corruption because the application might perform operations such as reading length fields or accessing byte arrays based on assumptions that do not hold true given the actual type received.
The operational impact of this vulnerability is severe, primarily affecting applications that utilize libsoup for WebSocket communication and implement handlers according to the public API specifications. Upon receiving a crafted Pong frame from an attacker-controlled server or man-in-the-middle position, these applications can experience immediate crashes due to segmentation faults resulting from invalid memory access. More dangerously, sophisticated exploitation could lead to heap corruption, potentially allowing arbitrary code execution if the attacker can control the contents of the malformed data and leverage specific allocator behaviors within the target environment. This undermines both the confidentiality and integrity aspects of security for any service relying on this library for real-time communication channels.
From a classification perspective, this vulnerability aligns with CWE-20 Improper Input Validation as it involves failing to properly validate or handle input types that do not match expected formats. It also relates closely to CWE-835 Loop with Unreachable Exit Condition if the corruption leads to infinite loops during memory management operations, and potentially CWE-416 Use After Free if the type confusion causes premature deallocation of resources. In terms of adversary tactics, this could be leveraged within MITRE ATT&CK technique T1059 Command and Scripting Interpreter or T1203 Exploitation for Client Execution, depending on how the resulting crash or code execution is utilized by an attacker to compromise a client-side application.
Mitigation strategies should focus primarily on updating libsoup to versions where this type mismatch has been corrected in the source code. Developers must ensure that their build environments are configured to pull these patched releases automatically through dependency management tools. For applications currently running unpatched versions, temporary workarounds might involve implementing custom signal handlers that perform explicit type checking before processing data, although this is not a robust long-term solution since it places additional burden on the application developer rather than fixing the root cause in the library itself. Additionally, enabling strict compiler warnings and static analysis tools can help identify similar API misuse patterns early in the development lifecycle to prevent such discrepancies from reaching production environments.