CVE-2026-27243: Adobe Connect Reflected XSS Vulnerability

CVE-2026-27243 Overview

CVE-2026-27243 is a reflected Cross-Site Scripting (XSS) vulnerability affecting Adobe Connect, a widely-used web conferencing platform. This vulnerability allows attackers to execute malicious JavaScript code within the context of a victim's browser by convincing them to visit a specially crafted URL referencing a vulnerable page. The vulnerability has a changed scope, meaning the impact extends beyond the vulnerable component to affect other resources within the browser context.

Critical Impact

Successful exploitation enables attackers to execute arbitrary JavaScript in the victim's browser session, potentially leading to session hijacking, credential theft, and unauthorized actions within Adobe Connect meetings and administrative interfaces.

Affected Products

• Adobe Connect version 2025.3 and earlier
• Adobe Connect version 12.10 and earlier

Discovery Timeline

• 2026-04-14 - CVE-2026-27243 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2026-27243

Vulnerability Analysis

This reflected XSS vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation) occurs when Adobe Connect fails to properly sanitize user-supplied input before reflecting it back to the browser. The vulnerability has a changed scope indicator, meaning that while the vulnerable component is Adobe Connect's web application, the security impact extends to other domains or resources accessible within the victim's browser session.

The attack requires user interaction—specifically, the victim must click on a malicious link containing the XSS payload. Once executed, the malicious script runs with the same privileges as the victim's session, potentially allowing the attacker to access sensitive meeting data, impersonate users, or perform administrative actions if the victim has elevated privileges.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and output encoding within Adobe Connect's web application. Specifically, user-controllable input parameters are reflected in the application's response without proper sanitization, allowing attackers to inject malicious script content that executes in the victim's browser.

Attack Vector

The attack is conducted over the network and requires an attacker to craft a malicious URL containing JavaScript payload. The attacker must then use social engineering techniques to convince a victim to click the link—typically through phishing emails, instant messages, or embedding the link in seemingly legitimate content.

Once the victim clicks the malicious URL, their browser loads the vulnerable Adobe Connect page, which reflects the attacker's JavaScript payload without proper encoding. The malicious script then executes within the security context of the Adobe Connect application, enabling the attacker to:

• Steal session cookies and authentication tokens
• Capture keystrokes and form data
• Modify page content to display fraudulent information
• Redirect users to malicious sites
• Perform actions on behalf of the authenticated user

Detection Methods for CVE-2026-27243

Indicators of Compromise

• Unusual URL patterns in web server logs containing encoded JavaScript payloads targeting Adobe Connect endpoints
• Unexpected script tags or event handlers in URL query parameters referencing Adobe Connect pages
• Reports from users about suspicious links or unexpected behavior during Adobe Connect sessions

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block reflected XSS patterns targeting Adobe Connect
• Monitor access logs for requests containing suspicious encoded characters or script-related keywords in URL parameters
• Deploy browser-based security solutions that can detect and block XSS attacks in real-time

Monitoring Recommendations

• Enable detailed logging on Adobe Connect servers to capture full request URIs
• Set up alerting for anomalous patterns such as high volumes of requests with encoded payloads from single sources
• Monitor user reports and help desk tickets for suspicious activity related to Adobe Connect links

How to Mitigate CVE-2026-27243

Immediate Actions Required

• Apply the security update from Adobe as soon as available per Adobe Security Advisory APSB26-37
• Educate users about the risks of clicking untrusted links, especially those claiming to lead to Adobe Connect meetings
• Implement Content Security Policy (CSP) headers to restrict script execution sources
• Consider temporarily restricting access to Adobe Connect to trusted networks until patching is complete

Patch Information

Adobe has released security updates addressing this vulnerability. Organizations should consult the Adobe Security Advisory APSB26-37 for specific patch details and update instructions. Upgrading to the latest patched version of Adobe Connect is the recommended remediation.

Workarounds

• Implement a Web Application Firewall (WAF) with XSS filtering rules as a defense-in-depth measure
• Deploy Content Security Policy (CSP) headers to restrict inline script execution and limit script sources
• Use browser extensions or endpoint protection solutions that provide XSS mitigation capabilities
• Restrict Adobe Connect access to known IP ranges or VPN connections to reduce external attack surface

# Example Content Security Policy header configuration for Apache
# Add to Apache configuration or .htaccess file
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"