CVE-2021-25267 in Sophos
Summary
by MITRE • 05/05/2022
Multiple XSS vulnerabilities in Webadmin allow for privilege escalation from admin to super-admin in Sophos Firewall older than version 19.0 GA.
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Analysis
by VulDB Data Team • 05/08/2022
The vulnerability identified as CVE-2021-25267 represents a critical cross-site scripting weakness within the Webadmin interface of Sophos Firewall systems prior to version 19.0 GA. This flaw exists in the administrative web interface component that manages user permissions and access controls, creating a pathway for malicious actors to exploit the system's privilege management mechanisms. The vulnerability specifically affects the authentication and authorization handling within the web administration portal, where insufficient input validation and output encoding allow crafted malicious payloads to be executed in the context of administrative sessions.
The technical exploitation of this vulnerability leverages stored cross-site scripting conditions that occur when administrative users interact with improperly sanitized input fields within the Webadmin interface. When an attacker successfully injects malicious javascript code through vulnerable parameters, this code executes within the browser context of authenticated administrative sessions. The flaw stems from inadequate sanitization of user-supplied data in the privilege escalation pathways, particularly affecting the administrative role assignment and permission modification functions. This vulnerability operates under the CWE-79 classification for cross-site scripting, specifically targeting the stored variant where malicious content is permanently stored and later executed without proper validation or encoding mechanisms.
The operational impact of this vulnerability extends beyond simple code execution to encompass full administrative compromise and privilege escalation from standard administrator to super-administrator level. Once exploited, attackers can manipulate user permissions, modify firewall rules, access sensitive network data, and potentially gain complete control over the protected network infrastructure. The attack surface is particularly concerning as it targets the administrative interface where all critical system functions are managed, enabling unauthorized access to network security controls and configuration parameters. This vulnerability undermines the fundamental security model of the Sophos Firewall by allowing lateral movement and privilege elevation without requiring additional authentication credentials.
Security practitioners should implement immediate mitigations including applying the latest firmware updates from Sophos to address the identified XSS vulnerabilities in the Webadmin interface. Network segmentation and access control measures should be reinforced to limit administrative access to the Webadmin interface, while implementing additional monitoring for suspicious administrative activities. The vulnerability demonstrates the importance of proper input validation and output encoding in administrative web interfaces, aligning with ATT&CK technique T1078 for valid accounts and T1548 for abuse of privileges. Organizations should conduct comprehensive security assessments of their administrative interfaces, implement web application firewalls to detect and prevent XSS payloads, and establish strict access control policies for administrative functions. Regular security testing of administrative interfaces should be performed to identify similar vulnerabilities that could enable privilege escalation attacks and maintain the integrity of network security controls.