Skip to main content
P
pauline.delacruz
Employee
December 1, 2025

KB-2387 421 redirect issue caused by AWS HTTPD patching

  • December 1, 2025
  • 0 replies
  • 6 views

Symptoms

After upgrading Apache httpd to version 2.4.63 or later, users may see the following error when accessing their environments that use an AWS Application Load Balancer (ALB):

421 Misdirected Request: The client needs a new connection for this request as the requested host name does not match the Server Name Indication (SNI) in use for this connection.

Cause

A change introduced in Apache httpd 2.4.63 (and versions after) affects how the server handles SNI matching for connections routed through an AWS ALB, causing Apache to reject requests with a 421 Misdirected Request.

This is a known incompatibility between Apache httpd 2.4.63+ and AWS ALB configurations. The issue is documented in the AWS community forum: Misdirected Request with Apache 2.4.52+ behind ALB.

Action

The recommended resolution is to revert the Apache httpd upgrade to a version prior to 2.4.63.

Affected Versions

This article applies to all self-managed versions of Appian using Apache httpd 2.4.63 and later, and have ALB in their environment.

Last Reviewed: June 2026

Terms & ConditionsAccessibility statement