CVE-2026-46382: Meeting Room Booking System SSRF Vulnerability

CVE-2026-46382 Overview

CVE-2026-46382 is a Server-Side Request Forgery (SSRF) vulnerability in the Meeting Room Booking System (MRBS), a PHP-based application for booking meeting rooms. Versions prior to 1.12.2 accept a user-supplied private or local Uniform Resource Identifier (URI) and fetch it without validation. An unauthenticated attacker can coerce the server into issuing HTTP requests to internal hosts, cloud metadata endpoints, or other resources reachable from the application host. The maintainers released version 1.12.2 to fix the flaw. The weakness is classified under CWE-918: Server-Side Request Forgery.

Critical Impact
Unauthenticated attackers can force the MRBS server to fetch arbitrary internal URIs, enabling reconnaissance of internal networks and access to protected services.

Affected Products

Meeting Room Booking System (MRBS) versions prior to 1.12.2
PHP-based deployments of the mrbs-code package
All installations exposing the affected URI-fetching endpoint to network callers

Discovery Timeline

2026-08-13 - CVE-2026-46382 published to the National Vulnerability Database (NVD)
2026-08-13 - Last updated in NVD database
Fix released - MRBS v1.12.2 published with remediation
Advisory published - GitHub Security Advisory GHSA-gh77-mpcm-f8r3

Technical Details for CVE-2026-46382

Vulnerability Analysis

MRBS accepts a URI from user-controlled input and passes it directly to a server-side fetch routine. The application performs no allowlist checks, no scheme restrictions, and no destination filtering before issuing the outbound request. As a result, an attacker can point the fetch at internal-only endpoints such as http://127.0.0.1, http://169.254.169.254 (cloud metadata service), or private RFC1918 address ranges.

The response content, headers, or timing behavior can be observed by the attacker in many SSRF scenarios. This exposes internal service banners, configuration data, and cloud instance credentials. The confidentiality of internal resources is the primary asset at risk, consistent with the vector's high impact on integrity of application-mediated requests.

Root Cause

The root cause is missing input validation on a URI parameter that reaches an HTTP client function. The fix in MRBS 1.12.2 introduces checks that reject private, local, and non-HTTP(S) targets before the fetch is executed. Consult the GitHub Security Advisory GHSA-gh77-mpcm-f8r3 for the specific code paths involved.

Attack Vector

Exploitation is remote and requires no authentication or user interaction. An attacker submits a crafted request containing a URI targeting an internal resource. The MRBS backend fetches the URI and, depending on the endpoint, may return response content to the caller. Typical targets include cloud instance metadata services, internal administrative interfaces, and localhost-bound services such as databases or caches.

No public proof-of-concept has been published at the time of NVD publication. Refer to the vendor advisory for technical details on the vulnerable parameter and fetch routine.

Detection Methods for CVE-2026-46382

Indicators of Compromise

Outbound HTTP requests from the MRBS web server process to internal IP ranges (RFC1918, 127.0.0.0/8, 169.254.0.0/16)
Web server access logs containing requests with URI parameters referencing localhost, internal hostnames, or cloud metadata addresses
Unexpected requests originating from the MRBS host to cloud metadata endpoints such as http://169.254.169.254/latest/meta-data/

Detection Strategies

Inspect MRBS request logs for user-supplied parameters containing URL schemes (http://, https://, file://, gopher://) pointing to non-public destinations
Correlate PHP-FPM or Apache/Nginx process network activity with expected outbound destinations; alert on connections to private ranges
Deploy egress filtering telemetry to identify the MRBS host initiating unusual internal reconnaissance patterns

Monitoring Recommendations

Enable verbose HTTP client logging in PHP to capture destination URIs for every outbound request initiated by MRBS
Forward web server, PHP, and network flow logs to a centralized analytics platform for correlation across the fetch behavior
Alert on repeated fetches to sequential internal IP addresses, which indicates active SSRF-based reconnaissance

How to Mitigate CVE-2026-46382

Immediate Actions Required

Upgrade MRBS to version 1.12.2 or later using the official GitHub release
Restrict outbound network access from the MRBS host to only the destinations required for legitimate operation
Review web server logs for evidence of prior exploitation attempts targeting URI parameters

Patch Information

The MRBS maintainers fixed this vulnerability in version 1.12.2. Administrators should apply the upgrade immediately, as the advisory states no workarounds are available. Verify the deployed version after upgrade and confirm the fetch validation logic is active.

Workarounds

No official workarounds exist per the vendor advisory; upgrading to 1.12.2 is required
As a compensating control, place MRBS behind egress firewall rules that block requests to private IP ranges and cloud metadata endpoints
Configure an outbound HTTP proxy with allowlisting to prevent SSRF payloads from reaching internal destinations