EC
463
HTTPERRORNotable4xx Client Error (Unofficial)HIGH confidence

Too Many Forwarded IP Addresses

Production Risk

Low — typically only occurs with misconfigured proxy chains or header spoofing attempts.

What this means

463 is used by AWS Application Load Balancer to indicate that the X-Forwarded-For header contained too many IP addresses. AWS ALB limits the number of IPs in this header and rejects requests that exceed the limit.

Why it happens
  1. 1The X-Forwarded-For header has more than the ALB-supported number of IP entries (typically more than 30).
  2. 2The request passed through many proxy layers or a misconfigured proxy chain that appended excessive IPs.
  3. 3A client or intermediary is spoofing the X-Forwarded-For header with many IP addresses.
How to reproduce

A request routed through many proxies arrives at AWS ALB with a very long X-Forwarded-For header.

trigger — this will error
trigger — this will error
GET /api/data HTTP/1.1
Host: myapp.elb.amazonaws.com
X-Forwarded-For: 1.1.1.1, 2.2.2.2, 3.3.3.3, ... (30+ IPs)

expected output

HTTP/1.1 463 (AWS ALB rejects the request)

Fix

Trim the X-Forwarded-For header in upstream proxies

WHEN Legitimate proxy chains are building up too many IPs.

Trim the X-Forwarded-For header in upstream proxies
# nginx — truncate X-Forwarded-For to last 2 hops
proxy_set_header X-Forwarded-For $remote_addr;

Why this works

Resets the X-Forwarded-For chain to just the direct client IP, preventing accumulation.

What not to do

✕ Do not blindly pass X-Forwarded-For through every proxy

Each proxy appending its own value can exceed the ALB limit.

Version notes
AWS ALB

AWS Application Load Balancer specific. Not a standard IETF code.

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