KB-2387 421 redirect issue caused by AWS HTTPD patching

pauline.delacruz — Tue, 30 Jun 2026 19:25:50 GMT

Current Revision posted to Appian Knowledge Base by pauline.delacruz on 6/30/2026 7:25:50 PM

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

Tags: known issues, apache, infrastructure

[DRAFT SUPP-1739] 421 redirect issue caused by AWS HTTPD patching

kaitlyn.wee — Wed, 03 Jun 2026 20:05:55 GMT

Revision 7 posted to Appian Knowledge Base by kaitlyn.wee on 6/3/2026 8:05:55 PM

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

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

Tags: known issues, apache, infrastructure

[DRAFT SUPP-1739] 421 redirect issue caused by AWS HTTPD patching

kaitlyn.wee — Wed, 03 Jun 2026 20:05:16 GMT

Revision 6 posted to Appian Knowledge Base by kaitlyn.wee on 6/3/2026 8:05:16 PM

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

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

Tags: known issues, apache, infrastructure

[DRAFT SUPP-1739] 421 redirect issue caused by AWS HTTPD patching

kaitlyn.wee — Wed, 03 Jun 2026 20:01:29 GMT

Revision 5 posted to Appian Knowledge Base by kaitlyn.wee on 6/3/2026 8:01:29 PM

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

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

Tags: known issues, apache, infrastructure

[DRAFT SUPP-1739] 421 redirect issue caused by AWS HTTPD patching

pauline.delacruz — Wed, 03 Jun 2026 19:58:50 GMT

Revision 4 posted to Appian Knowledge Base by pauline.delacruz on 6/3/2026 7:58:50 PM

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 behavioral change introduced in Apache httpd 2.4.63 (and versions after 2.4.62) affects how the server handles SNI matching for connections routed through an AWS ALB. The ALB's connection reuse behavior conflicts with the stricter SNI validation in newer Apache versions, causing Apache to reject requests with a 421 redirect.

This is a known incompatibility between Apache httpd 2.4.63+ and AWS ALB configurations, and is not caused by anything within Appian itself. 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

Tags: known issues, apache, infrastructure

[DRAFT SUPP-1739] 421 redirect issue caused by AWS HTTPD patching

kaitlyn.wee — Wed, 03 Jun 2026 19:55:11 GMT

Revision 3 posted to Appian Knowledge Base by kaitlyn.wee on 6/3/2026 7:55:11 PM

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

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: Month YYYY

Tags: known issues, apache, infrastructure

[DRAFT SUPP-1739] 421 redirect issue caused by AWS HTTPD patching

kaitlyn.wee — Wed, 03 Jun 2026 19:43:11 GMT

Revision 2 posted to Appian Knowledge Base by kaitlyn.wee on 6/3/2026 7:43:11 PM

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

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: Month YYYY

Tags: known issues, apache, infrastructure

[DRAFT SUPP-1739] 421 redirect issue caused by AWS HTTPD patching

pauline.delacruz — Mon, 01 Dec 2025 22:25:44 GMT

Revision 1 posted to Appian Knowledge Base by pauline.delacruz on 12/1/2025 10:25:44 PM

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Affected Versions

This article applies to all self-managed versions of Appian.

Last Reviewed: December 2025