An DevOps engineer is receiving reports that users can no longer access the company's web application after hardening of a web server. The users are…

The error ERRSSLVERSIONORCIPHERMISMATCH indicates that the client (user's browser) and the web server failed to agree on a common security protocol (TLS/SSL version) or cipher suite during the initial handshake. The context of "hardening" a web server strongly implies that older, less secure protocols like SSLv3, TLS 1.0, and TLS 1.1 were disabled. This action, while improving security, can cause this specific error if clients are using outdated browsers that do not support modern protocols. The most direct resolution is to ensure the server is correctly configured to use a secure and widely supported protocol, such as TLS 1.2 or the newer TLS 1.3.

A. Restarting the web server will not fix a fundamental configuration mismatch between the client and server's supported TLS/SSL protocols.
C. Updating the web server software is a good practice but does not directly address a specific configuration change made during hardening. The issue is the configuration, not an outdated server version.
D. Reviewing WAF logs is a diagnostic step, not a resolution. The problem is explicitly stated to be on the hardened web server, making a TLS configuration issue the most direct cause.

1. National Institute of Standards and Technology (NIST). (2019). Special Publication 800-52r2: Guidelines for the Selection

Configuration

and Use of Transport Layer Security (TLS) Implementations.

Section 3.1

Protocol Versions: "Servers that support TLS 1.2 shall be configured to use TLS 1.2

and servers that support TLS 1.3 should be configured to use TLS 1.3. ... SSL 2.0

SSL 3.0

TLS 1.0

and TLS 1.1 shall not be used." This guideline is a common basis for server hardening

and disabling these older protocols directly leads to the mismatch error if clients do not support TLS 1.2 or newer.

2. The Apache Software Foundation. (n.d.). Apache HTTP Server Version 2.4 Documentation: modssl.

Section: SSLProtocol Directive: The documentation explains how to configure supported protocols. A common hardening configuration is SSLProtocol all -SSLv3 -TLSv1 -TLSv1.1

which explicitly disables older versions. This demonstrates that the protocol version is a direct configuration setting that is modified during hardening and is the root cause of the mismatch error.

3. Mozilla. (n.d.). Security/Server Side TLS. Mozilla Wiki.

Section: Modern compatibility: This widely-respected industry guide states

"For services with clients that support TLS 1.3 and 1.2

and do not need backward compatibility... This is the recommended configuration for modern clients." It then provides configuration examples that disable TLS 1.0 and 1.1

directly linking the hardening practice to the configuration of specific TLS versions.