EXECUTIVE SUMMARY:
CVE-2026-40542 with a CVSS score of 9.8 is a critical authentication bypass vulnerability in Apache HttpClient 5.6, a widely used Java-based HTTP communication library. The flaw targets the SCRAM-SHA-256 authentication protocol, which could allow attackers to trick clients into establishing insecure connections by causing a missing critical verification step during the authentication process. Specifically, when a client attempts to use SCRAM-SHA-256 to log into a server, an attacker can cause the client to accept the authentication "success" without the client properly verifying the server's response, effectively impersonating a legitimate server and leading the client to believe it is communicating with a trusted source when it is not. This bypass can have a cascading effect on the security of enterprise data pipelines, potentially leading to unauthorized access and data breaches. An attacker requires access to the client-side application using HttpClient, as well as the ability to manipulate the authentication process, to exploit this vulnerability. As a result, a successful attack would grant the attacker the capability to intercept and manipulate sensitive data, posing significant business impact and consequences, including compromised data integrity and trust in the system.[/subscribe_to_unlock_form]
EXECUTIVE SUMMARY:
CVE-2026-40542 with a CVSS score of 9.8 is a critical authentication bypass vulnerability in Apache HttpClient 5.6, a widely used Java-based HTTP communication library. The flaw targets the SCRAM-SHA-256 authentication protocol, which could allow attackers to trick clients into establishing insecure connections by causing a missing critical verification step during the authentication process. Specifically, when a client attempts to use SCRAM-SHA-256 to log into a server, an attacker can cause the client to accept the authentication "success" without the client properly verifying the server's response, effectively impersonating a legitimate server and leading the client to believe it is communicating with a trusted source when it is not. This bypass can have a cascading effect on the security of enterprise data pipelines, potentially leading to unauthorized access and data breaches. An attacker requires access to the client-side application using HttpClient, as well as the ability to manipulate the authentication process, to exploit this vulnerability. As a result, a successful attack would grant the attacker the capability to intercept and manipulate sensitive data, posing significant business impact and consequences, including compromised data integrity and trust in the system.[emaillocker id="1283"]
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REFERENCES:
The following reports contain further technical details:
https://securityonline.info/apache-httpclient-auth-bypass-cve-2026-40542-scram-sha-256/