Heap Buffer Overflow in libsoup WebSocket Extension

Executive Summary

This vulnerability is a heap buffer overflow in libsoup's WebSocket implementation. When the permessage-deflate extension compresses a very large outgoing message, incorrect size calculations can cause zlib to write past the allocated buffer. This happens because truncated size values wrap around, leading to memory corruption.

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Detection Guidance

Detecting this vulnerability requires checking for affected libsoup versions and WebSocket configurations. Inspect installed libsoup packages using commands like 'rpm -qa | grep libsoup' on RPM-based systems or 'dpkg -l | grep libsoup' on Debian-based systems. Monitor WebSocket traffic for large messages with permessage-deflate enabled. Use network scanners to identify WebSocket endpoints and their compression settings.

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Impact Analysis

This flaw could allow attackers to corrupt memory, crash applications, or potentially execute arbitrary code if exploited. It may also lead to denial of service by causing targeted systems to fail. Exploitation requires a very large outgoing WebSocket message with the permessage-deflate extension enabled.

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Mitigation Strategies

Disable the permessage-deflate WebSocket extension if not required. Cap outgoing message sizes to prevent large payloads. Upgrade libsoup to version 3.7.3 or later. Apply vendor patches if available. Monitor systems for crashes or memory corruption that may indicate exploitation attempts.

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