CVE-2025-32049: libsoup WebSocket DoS Vulnerability

CVE-2025-32049 Overview

A denial of service vulnerability has been discovered in libsoup, the GNOME HTTP client/server library. The flaw exists in the SoupWebsocketConnection component, which may accept an excessively large WebSocket message without proper size validation. When processing such oversized messages, libsoup allocates memory without appropriate limits, leading to resource exhaustion and a denial of service condition.

Critical Impact

Remote attackers can exploit this vulnerability over the network without authentication to cause service disruption by exhausting system memory through malicious WebSocket messages.

Affected Products

• libsoup (GNOME HTTP library)
• Applications utilizing SoupWebsocketConnection for WebSocket functionality
• Red Hat Enterprise Linux and derivative distributions using affected libsoup versions

Discovery Timeline

• 2025-04-03 - CVE-2025-32049 published to NVD
• 2025-11-18 - Last updated in NVD database

Technical Details for CVE-2025-32049

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The SoupWebsocketConnection implementation in libsoup fails to properly enforce maximum message size restrictions when handling incoming WebSocket data frames. An attacker can exploit this weakness by sending specially crafted WebSocket messages with large payloads.

When libsoup receives an oversized WebSocket message, it attempts to allocate sufficient memory to buffer the entire message content. Without proper size validation or memory allocation limits, this behavior can be exploited to force the library to consume excessive amounts of system memory. In scenarios where multiple malicious connections are established or repeated large messages are sent, the accumulated memory consumption can exhaust available system resources.

The network-based attack vector makes this vulnerability particularly concerning for services that expose WebSocket endpoints to untrusted clients. Since no authentication or user interaction is required, any network-accessible application using vulnerable libsoup versions is at risk.

Root Cause

The root cause of this vulnerability is the absence of proper message size validation and memory allocation throttling in the SoupWebsocketConnection component. The implementation accepts and attempts to buffer WebSocket messages without enforcing reasonable size constraints, allowing unbounded memory allocation based on attacker-controlled input.

Attack Vector

An attacker can exploit this vulnerability remotely over the network by establishing a WebSocket connection to a vulnerable libsoup-based application and sending large WebSocket frames or messages. The attack requires no authentication or special privileges, making it accessible to any network-connected adversary.

The exploitation mechanism involves:

1. Establishing a WebSocket connection to the target application
2. Sending one or more WebSocket messages with excessively large payloads
3. The vulnerable SoupWebsocketConnection attempts to allocate memory for the entire message
4. Repeated or sustained attacks exhaust available memory, causing denial of service

Technical details regarding specific exploitation methods can be found in the Red Hat Bug Report #2357066 and the Red Hat CVE Analysis.

Detection Methods for CVE-2025-32049

Indicators of Compromise

• Abnormal memory consumption in processes using libsoup or SoupWebsocketConnection
• Unusually large WebSocket messages observed in network traffic analysis
• Application crashes or out-of-memory errors in libsoup-dependent services
• High volume of WebSocket connections from suspicious IP addresses

Detection Strategies

• Monitor system memory utilization for processes that implement WebSocket functionality using libsoup
• Implement network-level inspection for WebSocket frames exceeding expected size thresholds
• Configure application-level logging to track WebSocket message sizes and connection patterns
• Use SentinelOne Singularity Platform to detect anomalous process behavior indicative of memory exhaustion attacks

Monitoring Recommendations

• Establish baseline memory consumption for libsoup-dependent applications and alert on significant deviations
• Deploy network monitoring to identify and flag unusually large WebSocket payloads
• Configure rate limiting on WebSocket endpoints to prevent rapid connection establishment from single sources
• Review application logs for patterns of WebSocket-related errors or memory allocation failures

How to Mitigate CVE-2025-32049

Immediate Actions Required

• Apply security patches from your distribution vendor as soon as they become available
• Review and update libsoup packages to patched versions referenced in Red Hat Security Advisories
• Implement network-level controls to limit WebSocket message sizes at the load balancer or reverse proxy layer
• Consider temporarily disabling WebSocket functionality in critical applications if patches cannot be immediately applied

Patch Information

Red Hat has released multiple security advisories addressing this vulnerability across various product versions. Organizations should consult the following advisories for patching guidance:

• RHSA-2025:21657
• RHSA-2025:8126
• RHSA-2025:8128
• RHSA-2025:8132
• RHSA-2025:8139
• RHSA-2025:8140
• RHSA-2025:8252
• RHSA-2025:8480
• RHSA-2025:8481
• RHSA-2025:8482
• RHSA-2025:8663
• RHSA-2025:9179

Workarounds

• Configure reverse proxy or load balancer rules to enforce maximum WebSocket frame and message sizes
• Implement application-level message size validation before passing data to libsoup components
• Deploy network segmentation to restrict WebSocket endpoint exposure to trusted networks only
• Use connection rate limiting to reduce the impact of sustained denial of service attempts

# Example: Nginx configuration to limit WebSocket message size
# Add to nginx.conf or server block configuration
proxy_read_timeout 300s;
proxy_send_timeout 300s;
proxy_buffer_size 64k;
proxy_buffers 8 64k;
client_max_body_size 1m;