Authentication Bypass Vulnerability in Apache Tomcat

CVE-2026-65905

What is CVE-2026-65905?

CVE-2026-65905 is a notable authentication bypass vulnerability found within the Apache Tomcat server, an open-source implementation of the Java Servlet and JavaServer Pages technologies used widely in enterprise applications. The vulnerability specifically affects the DIGEST authenticator component, allowing an attacker to exploit a flaw in the nonce management. When a client makes a DIGEST authenticated request with a nonceCount that maximally approaches the replay window limit, this request may be replayed once while the nonceCount remains valid in that window. Consequently, this could enable unauthorized users to gain access to sensitive functions or data without proper authentication if certain request conditions are met. Apache Tomcat is pivotal in many web application infrastructures, making this vulnerability a critical concern for organizations relying on its services.

Potential impact of CVE-2026-65905

1. Unauthorized Access: This vulnerability allows an attacker to bypass authentication mechanisms, potentially granting them unauthorized access to sensitive resources or administrative functionalities. This could lead to data exposure, modification, or exploitation of sensitive information.

2. System Compromise: With the ability to authenticate bypassing the built-in security controls, attackers may escalate their privileges or execute unauthorized commands. This could facilitate further attacks, including the installation of malware or the manipulation of application behavior.

3. Increased Risk of Data Breach: Organizations affected by this vulnerability may be at a higher risk of data breaches, as unauthorized access could lead to the extraction of confidential user data, business-critical information, or intellectual property. The ramifications of such breaches could result in significant financial penalties and damage to reputation.

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