Executive Summary

CVE-2025-11276 is a stored cross-site scripting (XSS) vulnerability in the Rebuild software up to version 4.1.3, specifically in the Comment/Guestbook component. It occurs because user input is not properly neutralized before being included in web pages, allowing an attacker to inject malicious JavaScript code. This code executes in the browsers of other users who view the affected comments, potentially compromising data integrity. The attack can be initiated remotely and requires victim interaction. The vendor has fixed this issue in version 4.1.4. [1, 2]

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Impact Analysis

This vulnerability can allow attackers to execute arbitrary JavaScript in the browsers of users who view the malicious comments. Potential impacts include theft of cookies, session hijacking, cross-site request forgery (CSRF) using administrator sessions, privilege escalation, and persistent site compromise if the injected scripts perform actions with admin privileges. This can lead to unauthorized actions and compromise of user accounts and site integrity. [2]

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Detection Guidance

Detection can involve checking for the presence of malicious stored scripts in the Comment/Guestbook component of Rebuild versions up to 4.1.3. One approach is to review user-submitted comments for suspicious payloads such as <svg/onload=alert(document.cookie)>. You can use web application scanning tools that detect stored XSS vulnerabilities or manually query the database or web interface for comments containing suspicious HTML or JavaScript tags. For example, using grep or similar commands on exported comment data: grep -i '<svg' comments.txt. Additionally, monitoring HTTP requests and responses for injected scripts or unusual payloads in comment submissions can help detect exploitation attempts. [2]

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Mitigation Strategies

Immediate mitigation steps include upgrading the Rebuild software to version 4.1.4, which contains the fix for this vulnerability. Additionally, apply proper output escaping such as HTML entity encoding of characters like <, >, &, and ". Implement contextual output encoding and use strict allowlist sanitizers like HTMLPurifier if HTML input is allowed. Disallow inline event handlers and <svg> tags in user inputs. Perform server-side validation to neutralize dangerous tags and attributes before storing comments. Ensure all administrative views and summary widgets perform output encoding to prevent script execution. [2]

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