CVE-2025-27405 Overview
CVE-2025-27405 is a reflected cross-site scripting (XSS) vulnerability in Icinga Web 2, an open source monitoring web interface and framework. An attacker can craft a malicious URL that, when visited by an authenticated user, executes arbitrary JavaScript in the user's browser session. The injected code runs with the victim's privileges inside Icinga Web, allowing actions on their behalf. The flaw affects versions prior to 2.11.5 and 2.12.3 and is tracked under [CWE-79]. Fixed releases and a content security policy workaround for version 2.12.2 are available from the vendor.
Critical Impact
Successful exploitation lets an attacker execute arbitrary JavaScript in an Icinga Web 2 user's session and perform monitoring platform actions on their behalf.
Affected Products
- Icinga Web 2 versions prior to 2.11.5
- Icinga Web 2 versions 2.12.0 through 2.12.2
- Icinga Web 2 (component icinga:icinga_web_2)
Discovery Timeline
- 2025-03-26 - CVE-2025-27405 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-27405
Vulnerability Analysis
CVE-2025-27405 is a reflected XSS flaw ([CWE-79]) in the Icinga Web 2 monitoring interface. The application fails to properly sanitize or encode user-controlled input reflected back into rendered pages. An attacker crafts a URL containing a JavaScript payload and delivers it to a target user through phishing, chat, or another social channel. When an authenticated Icinga Web 2 user opens the URL, the injected script executes in their browser context.
The attacker gains the ability to read session state, issue API requests, and interact with the Icinga monitoring backend using the victim's session. Because Icinga Web 2 often provides visibility into infrastructure health and can trigger operational commands, session compromise here can affect monitoring integrity and incident response workflows.
Root Cause
The root cause is improper neutralization of input during web page generation. Content supplied through the URL is reflected into HTML output without adequate contextual output encoding, allowing HTML and JavaScript to break out of the intended data context and execute as script.
Attack Vector
Exploitation occurs over the network and requires user interaction. The attacker crafts a URL pointing to a vulnerable Icinga Web 2 instance and lures a signed-in user to click it. No attacker credentials are required. On execution, the payload runs in the origin of the Icinga Web 2 application, giving the attacker access to the victim's authenticated session cookies, forms, and any privileged UI actions available to that user.
No verified public proof-of-concept is available. See the Icinga GitHub Security Advisory GHSA-3x37-fjc3-ch8w for vendor technical details.
Detection Methods for CVE-2025-27405
Indicators of Compromise
- Web server access logs containing Icinga Web 2 URLs with encoded script fragments such as %3Cscript%3E, javascript:, onerror=, or onload= in query parameters.
- Unexpected outbound requests from user browsers to attacker-controlled domains immediately after loading an Icinga Web 2 page.
- Icinga Web 2 audit records showing actions performed by legitimate users at times inconsistent with normal activity.
Detection Strategies
- Inspect HTTP access logs on the Icinga Web 2 reverse proxy or application server for reflected payload patterns in query strings and referrer headers.
- Deploy a web application firewall (WAF) rule set that flags HTML tags, event handlers, and JavaScript URI schemes in requests to Icinga Web 2 endpoints.
- Correlate email or chat gateway logs for URLs targeting the Icinga Web 2 hostname combined with suspicious query parameters.
Monitoring Recommendations
- Enable and forward Icinga Web 2 application and audit logs to a central SIEM for retention and correlation.
- Alert on browser Content Security Policy (CSP) violation reports originating from the Icinga Web 2 origin.
- Monitor authenticated session activity for anomalies such as rapid configuration changes, new API tokens, or logins from unusual locations following URL clicks.
How to Mitigate CVE-2025-27405
Immediate Actions Required
- Upgrade Icinga Web 2 to version 2.11.5 or 2.12.3 (or later) as published by the vendor.
- Inventory all Icinga Web 2 instances, including staging and internal-only deployments, and confirm the running version.
- Instruct operators to avoid clicking Icinga Web 2 URLs received from untrusted sources until patching is complete.
Patch Information
Icinga has released fixed versions Icinga Web 2 v2.11.5 and Icinga Web 2 v2.12.3. Details are documented in the GitHub Security Advisory GHSA-3x37-fjc3-ch8w. Administrators should apply the upgrade using their package manager or download the release from the Icinga project.
Workarounds
- Users running Icinga Web 2 2.12.2 can enable a Content Security Policy (CSP) in the application settings to restrict inline script execution as a temporary control.
- Place Icinga Web 2 behind a reverse proxy or WAF that filters requests containing HTML or JavaScript tokens.
- Restrict Icinga Web 2 access to trusted networks or VPN users to reduce phishing exposure until the patch is applied.
# Configuration example: enable CSP workaround for Icinga Web 2.12.2
# In the Icinga Web 2 UI: Configuration > Application > Security
# Or edit /etc/icingaweb2/config.ini:
[security]
content_security_policy = "1"
# Verify upgraded version after applying the patch
icingacli --version
# Expected: 2.11.5 or 2.12.3 (or later)
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
