CVE-2021-0341 in Access Manager
Summary
by MITRE • 02/10/2021
In verifyHostName of OkHostnameVerifier.java, there is a possible way to accept a certificate for the wrong domain due to improperly used crypto. This could lead to remote information disclosure with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-8.1 Android-9 Android-10 Android-11Android ID: A-171980069
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Analysis
by VulDB Data Team • 11/13/2025
The vulnerability identified as CVE-2021-0341 resides within the SSL/TLS certificate verification mechanism of Android's networking stack, specifically in the OkHostnameVerifier.java implementation. This flaw represents a critical security weakness that could allow attackers to bypass domain validation during secure connections, potentially enabling man-in-the-middle attacks. The issue manifests in Android versions 8.1 through 11, affecting a significant portion of the mobile ecosystem where secure communications are paramount for protecting user data and maintaining trust in network transactions. The vulnerability stems from improper cryptographic validation logic that fails to correctly verify hostname matches against certificate subject alternative names and common names.
The technical root cause of this vulnerability lies in the flawed hostname verification algorithm that processes certificate validation during SSL/TLS handshakes. When a client establishes a secure connection to a server, the certificate verification process should rigorously validate that the presented certificate is intended for the domain being accessed. However, the implementation in OkHostnameVerifier.java contains a logic error that allows certain certificate patterns to pass validation even when they do not correspond to the expected domain. This flaw specifically affects the comparison operations used to match hostnames against certificate subject alternative names and common names, creating a pathway where malicious certificates could be accepted for incorrect domains. The vulnerability operates at the cryptographic protocol level, where the improper use of certificate validation functions undermines the fundamental security guarantee of domain authentication.
The operational impact of CVE-2021-0341 extends beyond simple certificate validation failures, potentially enabling sophisticated attacks that could compromise user privacy and data integrity. Attackers could exploit this vulnerability to perform man-in-the-middle attacks by presenting certificates for domains other than those intended, allowing them to intercept and potentially modify communications between users and legitimate services. This capability could lead to unauthorized access to sensitive information including personal data, financial transactions, and corporate communications. The vulnerability's impact is particularly severe because it operates without requiring any additional execution privileges or user interaction, making it highly exploitable across the affected Android versions. Network traffic that relies on SSL/TLS encryption for protection becomes vulnerable to interception and manipulation, potentially affecting all applications that utilize the Android networking stack for secure communications.
Security mitigation strategies for this vulnerability focus on both immediate remediation and long-term architectural improvements. The primary solution involves updating affected Android devices to versions that contain patched implementations of the certificate verification logic, with Google releasing security updates that correct the hostname validation algorithm. Organizations should also implement network monitoring to detect potential exploitation attempts and consider deploying additional security layers such as certificate pinning for critical applications. The vulnerability aligns with CWE-295, which addresses improper certificate validation, and maps to ATT&CK technique T1573.002 related to secure protocol violations. Additionally, security professionals should review application-level certificate validation implementations to ensure they do not rely on potentially compromised system libraries, and consider implementing more robust validation mechanisms that explicitly check for these specific edge cases in hostname matching algorithms.