CVE-2026-20102 in Secure Firewall Adaptive Security Appliance Software
Summary
by MITRE • 03/04/2026
A vulnerability in the SAML 2.0 single sign-on (SSO) feature of Cisco Secure Firewall ASA Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against the SAML feature and access sensitive, browser-based information.
This vulnerability is due to insufficient input validation of multiple HTTP parameters. An attacker could exploit this vulnerability by persuading a user to access a malicious link. A successful exploit could allow the attacker to conduct a reflected XSS attack through an affected device.
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Analysis
by VulDB Data Team • 03/05/2026
The vulnerability identified as CVE-2026-20102 represents a critical security flaw within the SAML 2.0 single sign-on implementation of Cisco's firewall software portfolio, specifically affecting Cisco Secure Firewall ASA Software and Cisco Secure Firewall Threat Defense (FTD) Software. This weakness exists in the authentication and session management mechanisms that govern how the software processes incoming HTTP requests during the SAML authentication flow, creating an exploitable entry point for malicious actors seeking to compromise user sessions and access sensitive information. The vulnerability's presence in the core SAML 2.0 SSO functionality means that any user interaction with the affected system during authentication could potentially expose them to attack vectors that bypass traditional authentication mechanisms.
The technical root cause of this vulnerability stems from inadequate input validation procedures applied to multiple HTTP parameters that are processed during the SAML authentication handshake. When the software receives HTTP requests containing SAML parameters, it fails to properly sanitize or validate the input data, allowing malicious payloads to be injected directly into the response handling mechanisms. This insufficient validation creates a reflected cross-site scripting vulnerability where attacker-controlled content can be executed within the browser context of authenticated users who interact with maliciously crafted links. The flaw specifically affects parameters that are used in the SAML assertion processing and redirect mechanisms, where unvalidated input is directly incorporated into HTTP responses without proper encoding or sanitization.
The operational impact of this vulnerability extends beyond simple XSS exploitation, as it enables attackers to conduct sophisticated session hijacking operations and access sensitive browser-based information that users have stored in their session cookies or local storage. An attacker could craft malicious links that, when clicked by an authenticated user, would execute malicious JavaScript code in the victim's browser context, potentially stealing session tokens, credentials, or other sensitive data. The reflected nature of the XSS attack means that the malicious payload is delivered through the application itself, making it particularly dangerous as it can bypass traditional security measures and appear to originate from legitimate system components. This vulnerability essentially undermines the trust model that SAML 2.0 is designed to establish between identity providers and service providers.
Organizations utilizing affected Cisco firewall software should immediately implement mitigations including input validation enforcement, HTTP parameter sanitization, and web application firewall rules to block suspicious parameter values. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and follows ATT&CK technique T1566.001 for spearphishing with attachments, as attackers would likely use malicious links to deliver the XSS payloads. Network segmentation and monitoring of SAML-related traffic should be enhanced to detect anomalous parameter patterns, while regular security assessments should verify that all HTTP parameters are properly validated before being processed by the SAML authentication system. Patch management procedures should be prioritized to ensure timely deployment of Cisco's security updates that address the insufficient input validation issues in the SAML implementation.