CVE-2026-4958 Overview
A vulnerability has been discovered in OpenBMB XAgent 1.0.0 that affects the ReplayServer.on_connect and ReplayServer.send_data functions within the WebSocket endpoint component. The vulnerability exists in the file XAgentServer/application/websockets/replayer.py and allows an attacker to bypass authorization controls through manipulation of the interaction_id argument. This authorization bypass vulnerability can be exploited remotely, though the attack complexity is reported as high and exploitability is considered difficult.
Critical Impact
Remote attackers can bypass authorization controls in the XAgent WebSocket endpoint by manipulating the interaction_id parameter, potentially gaining unauthorized access to replay functionality and sensitive interaction data.
Affected Products
- OpenBMB XAgent 1.0.0
Discovery Timeline
- 2026-03-27 - CVE-2026-4958 published to NVD
- 2026-03-30 - Last updated in NVD database
Technical Details for CVE-2026-4958
Vulnerability Analysis
This vulnerability is classified as CWE-285 (Improper Authorization), indicating a failure to properly validate user permissions before granting access to protected resources. The affected component is the WebSocket-based replay server functionality in XAgent, specifically the ReplayServer.on_connect and ReplayServer.send_data methods. When a WebSocket connection is established or data is transmitted, the application fails to adequately verify that the requesting user is authorized to access the specified interaction_id.
The vulnerability allows authenticated users to potentially access interaction data belonging to other users or sessions by providing arbitrary interaction_id values. This represents a horizontal privilege escalation scenario where authorization boundaries between different user interactions are not properly enforced.
Root Cause
The root cause of this vulnerability lies in insufficient authorization checks within the WebSocket endpoint handlers. The replayer.py file processes interaction_id parameters without adequately validating whether the authenticated user has permission to access the requested interaction. This missing authorization check allows users to enumerate and access interaction records that should be restricted based on ownership or role-based access control policies.
Attack Vector
The attack is network-based and requires the attacker to have low-level privileges (authenticated access) to the XAgent system. The exploitation involves:
- Establishing a WebSocket connection to the XAgent replay endpoint
- Manipulating the interaction_id parameter in WebSocket messages
- Bypassing authorization checks to access unauthorized interaction data
While the vulnerability is remotely exploitable, the attack complexity is high and successful exploitation is considered difficult due to the need for valid authentication credentials and understanding of the target system's interaction ID structure.
The vulnerability has been publicly disclosed with a proof-of-concept available. See the GitHub Gist PoC for technical details on the exploitation mechanism.
Detection Methods for CVE-2026-4958
Indicators of Compromise
- Unusual WebSocket connection patterns to the /replayer endpoint with varying interaction_id values
- Authentication logs showing users accessing interaction IDs outside their normal scope
- Elevated rates of WebSocket connection attempts from single authenticated sessions
- Log entries indicating access to interaction records not associated with the requesting user
Detection Strategies
- Monitor WebSocket endpoint logs for requests containing interaction_id parameters that don't match the authenticated user's session history
- Implement alerting for enumeration-style access patterns where sequential or random interaction_id values are being probed
- Deploy application-layer monitoring to track authorization failures and suspicious access patterns in the replay server component
- Review access logs for the XAgentServer/application/websockets/replayer.py handlers
Monitoring Recommendations
- Enable verbose logging for all WebSocket connections to the XAgent replay server
- Configure alerts for failed authorization attempts and unusual access patterns
- Implement rate limiting on the WebSocket endpoint to slow enumeration attempts
- Monitor for connections originating from unexpected network segments or geographies
How to Mitigate CVE-2026-4958
Immediate Actions Required
- Restrict network access to the XAgent WebSocket endpoint to trusted networks only
- Implement additional authentication layers for the replay server functionality
- Review and audit existing interaction access logs for signs of prior exploitation
- Consider disabling the replay server functionality if not critical to operations
Patch Information
The vendor (OpenBMB) was contacted early about this disclosure but did not respond. At the time of publication, no official patch is available. Organizations using XAgent 1.0.0 should implement the workarounds described below and monitor for vendor updates.
For additional technical details and threat intelligence, refer to:
Workarounds
- Implement network segmentation to restrict access to the XAgent WebSocket endpoint
- Add a reverse proxy or web application firewall with custom rules to validate interaction_id ownership before forwarding requests
- Deploy custom authorization middleware to enforce user-to-interaction ownership validation
- Consider implementing request signing or additional token validation for the replay endpoint
# Example: Restrict WebSocket endpoint access via iptables
# Allow only trusted internal networks to access XAgent WebSocket port
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
