CVE-2026-46688 Overview
CVE-2026-46688 is an open redirect vulnerability in the Meeting Room Booking System (MRBS), a PHP-based application used for reserving meeting rooms. The flaw exists in versions prior to 1.12.2 and allows unauthenticated attackers to craft URLs that redirect users to arbitrary external destinations. Attackers can leverage this behavior to deliver phishing pages that impersonate the legitimate MRBS login interface. The maintainers released version 1.12.2 to address the issue, and no workarounds are documented. The weakness is tracked under CWE-601: URL Redirection to Untrusted Site.
Critical Impact
Attackers can craft MRBS URLs that redirect authenticated or unauthenticated users to attacker-controlled sites, enabling credential phishing against MRBS installations.
Affected Products
- Meeting Room Booking System (MRBS) versions prior to 1.12.2
- MRBS installations reachable over the network
- Deployments that expose MRBS login flows to end users
Discovery Timeline
- 2026-08-13 - CVE-2026-46688 published to the National Vulnerability Database (NVD)
- 2026-08-13 - Last updated in NVD database
Technical Details for CVE-2026-46688
Vulnerability Analysis
MRBS accepts a redirect target as a query parameter without validating that the destination points to a trusted host. An unauthenticated request supplying an attacker-controlled URL causes the application to redirect the browser to that location. Because the initial URL belongs to a legitimate MRBS deployment, users have little visual indication of the redirection before authentication material is submitted to the attacker.
Open redirect flaws such as this typically appear when server-side code takes user-supplied input and passes it directly to an HTTP Location header or a client-side navigation call. The MRBS advisory confirms the redirect target is controlled through a query string value and can be set by any unauthenticated requester.
Root Cause
The root cause is insufficient validation of the redirect target parameter, categorized as CWE-601. MRBS did not enforce an allow-list of internal paths or validate that the target host matched the application's own domain before issuing the redirect.
Attack Vector
Exploitation occurs over the network with no privileges required, but the victim must interact with the malicious link. An attacker crafts a URL pointing at a real MRBS host with a redirect parameter set to a controlled domain. Delivery methods include email, chat platforms, or embedded links on other web pages. Once clicked, the browser is redirected to a spoofed MRBS login page where credentials can be harvested.
See the GitHub Security Advisory GHSA-6xcj-g522-859f for the maintainer's technical description.
Detection Methods for CVE-2026-46688
Indicators of Compromise
- Inbound HTTP requests to MRBS endpoints containing redirect query parameters that reference external hostnames.
- Web server access logs showing 3xx responses with Location headers pointing to domains other than the MRBS host.
- User reports of MRBS links resolving to unfamiliar login pages or unexpected domains.
Detection Strategies
- Parse MRBS web server logs for query parameters carrying URL-encoded external targets and flag off-domain redirects.
- Correlate MRBS URL clicks in email and proxy telemetry with subsequent connections to newly registered or low-reputation domains.
- Alert on MRBS authentication failures immediately followed by successful logins from atypical geolocations, which may indicate credential replay after phishing.
Monitoring Recommendations
- Ingest MRBS web server logs and reverse proxy logs into a centralized analytics platform for continuous inspection.
- Monitor outbound DNS and proxy traffic for lookalike domains referencing the organization's MRBS hostname.
- Track version banners of MRBS deployments to confirm all instances run 1.12.2 or later.
How to Mitigate CVE-2026-46688
Immediate Actions Required
- Upgrade all MRBS deployments to version 1.12.2 or later using the official v1.12.2 release.
- Inventory internet-exposed MRBS instances and prioritize patching those reachable by unauthenticated users.
- Notify staff who use MRBS to verify the browser address bar before submitting credentials to any MRBS login page.
Patch Information
The MRBS maintainers fixed the open redirect in version 1.12.2. Administrators should deploy the update from the MRBS GitHub repository release page and confirm the running version after upgrade. Details are described in GHSA-6xcj-g522-859f.
Workarounds
- No vendor-supplied workarounds are available; upgrading to 1.12.2 is the only remediation.
- As a compensating control, place MRBS behind a reverse proxy or web application firewall that strips or validates redirect parameters against an allow-list of internal paths.
- Enforce multi-factor authentication on MRBS accounts to reduce the impact of phishing-driven credential theft.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
