Traefik Ingress in AKS does not URL-decode route parameters consistently (special characters break routing)

Traefik Traefik v2
1

Problem Details:
When route parameters contain special or encoded characters, routing fails. Examples include:

  • Special characters

  • Encrypted strings

  • Base64 values (+, /, =)

  • Dots (.)

  • Encoded or unencoded slashes (/)

Traefik appears to treat some of these characters (especially /) as path separators instead of part of the parameter value.

Observed Behavior:

  • Requests that work locally (via Kestrel) fail when routed through Traefik

  • Traefik fails route matching

  • Backend application returns 400 Bad Request

  • Headers (including auth tokens) are valid and unchanged

Expected Behavior:

  • Route parameters should be passed to the backend exactly as encoded

  • URL decoding behavior should be consistent with standard HTTP handling (or configurable)

  • Encoded characters (e.g., %2F) should not break route matching

  1. Is there a configuration in Traefik to control URL decoding behavior for route parameters?

  2. Can Traefik be configured to preserve encoded slashes (%2F) instead of interpreting them as path separators?

  3. Are there recommended middlewares (e.g., ReplacePathRegex, StripPrefix, etc.) to handle this scenario?

  4. Is this expected behavior or a known limitation?

2

Have you tried http.encodedCharacters.allowEncodedSlash, are you on Traefik latest (old bug)?