CVE-2026-15501 Overview
CVE-2026-15501 is a Server-Side Request Forgery (SSRF) vulnerability [CWE-918] affecting AstrBotDevs AstrBot versions up to 4.25.2. The flaw resides in the ToolsRoute.test_mcp_connection function within astrbot/dashboard/routes/tools.py, part of the MCP Test Endpoint component. Attackers can manipulate the mcp_server_config.url argument to force the server into issuing arbitrary outbound requests. The vendor was notified before public disclosure but did not respond. A public proof-of-concept is available on GitHub.
Critical Impact
Authenticated remote attackers can coerce the AstrBot server to send HTTP requests to internal or external endpoints, enabling reconnaissance of internal networks and interaction with unauthenticated internal services.
Affected Products
- AstrBotDevs AstrBot versions up to and including 4.25.2
- Component: MCP Test Endpoint (astrbot/dashboard/routes/tools.py)
- Function: ToolsRoute.test_mcp_connection
Discovery Timeline
- 2026-07-12 - CVE-2026-15501 published to NVD
- 2026-07-15 - Last updated in NVD database
Technical Details for CVE-2026-15501
Vulnerability Analysis
The vulnerability exists in the AstrBot dashboard route that handles Model Context Protocol (MCP) connection testing. When a user submits a test request through the dashboard, the test_mcp_connection handler reads the mcp_server_config.url parameter and issues an HTTP request to that destination without validating the target. Because the server performs the request on behalf of the caller, attackers can pivot requests through the AstrBot backend to reach hosts and ports otherwise unreachable from the public internet.
Exploitation requires only low-privileged authenticated access and no user interaction. Successful abuse can reveal internal service banners, cloud metadata endpoints, and administrative interfaces that trust requests originating from localhost or the internal network.
Root Cause
The root cause is missing validation of the user-supplied URL in mcp_server_config.url. The handler does not enforce an allow-list of destinations, does not filter loopback or private address ranges, and does not restrict URL schemes. This maps directly to CWE-918: Server-Side Request Forgery.
Attack Vector
The attack vector is network-based and remote. An authenticated attacker submits a crafted MCP connection test containing a URL pointing to an internal resource such as http://127.0.0.1:admin-port/ or a cloud metadata service like http://169.254.169.254/. The AstrBot backend fetches the URL and, depending on the response handling, may reflect content or timing information back to the attacker.
A public proof-of-concept demonstrating the manipulation of mcp_server_config.url is hosted on GitHub. See the GitHub Gist PoC and the VulDB Vulnerability Details for additional context.
Detection Methods for CVE-2026-15501
Indicators of Compromise
- Outbound HTTP requests from the AstrBot process to 127.0.0.1, localhost, RFC1918 ranges, or link-local addresses such as 169.254.169.254.
- Access log entries for POST requests to the MCP test endpoint containing unexpected URL schemes or non-public hostnames in mcp_server_config.url.
- Repeated MCP test invocations from a single authenticated session targeting varying internal IPs or ports, indicating scanning behavior.
Detection Strategies
- Instrument the AstrBot application to log the full mcp_server_config.url value on every call to ToolsRoute.test_mcp_connection and alert on private or loopback destinations.
- Deploy egress network monitoring on the AstrBot host to flag connections from the application to non-approved internal networks.
- Correlate authenticated dashboard sessions with unusual bursts of outbound short-lived HTTP requests.
Monitoring Recommendations
- Enable web server access logging with full request bodies for dashboard routes under /dashboard/routes/tools.
- Forward AstrBot host process and network telemetry to a centralized data lake for retention and anomaly analysis.
- Alert on any request from the AstrBot service to cloud instance metadata endpoints.
How to Mitigate CVE-2026-15501
Immediate Actions Required
- Restrict access to the AstrBot dashboard to trusted administrators only and enforce strong authentication.
- Place the AstrBot server behind an egress proxy that blocks requests to loopback, RFC1918, and link-local address ranges.
- Disable the MCP Test Endpoint until a fixed version is available if the feature is not required.
Patch Information
As of the last NVD update on 2026-07-15, no vendor patch has been published. The vendor did not respond to the pre-disclosure contact. Monitor the AstrBot project for updates beyond version 4.25.2 and apply fixes as soon as they are released.
Workarounds
- Add an allow-list check in ToolsRoute.test_mcp_connection that validates mcp_server_config.url against approved external hostnames before issuing the request.
- Reject URLs that resolve to private, loopback, multicast, or link-local addresses, and enforce https scheme only.
- Run AstrBot in a network segment that cannot reach sensitive internal services or cloud metadata endpoints.
# Example egress restriction using iptables to block AstrBot from reaching metadata and loopback pivots
iptables -A OUTPUT -m owner --uid-owner astrbot -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -m owner --uid-owner astrbot -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner astrbot -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -m owner --uid-owner astrbot -d 192.168.0.0/16 -j REJECT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
