Werk #19429: check_cert: Proxy connection failing with HTTP/1.0 proxies

Component

Checks & agents

Title

check_cert: Proxy connection failing with HTTP/1.0 proxies

Date

Apr 16, 2026

Level

Trivial Change

Class

Bug Fix

Compatibility

Compatible - no manual interaction needed

Checkmk versions & editions

2.6.0b1 Not yet released	Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.5.0b5 Not yet released	Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

Previously, the Check certificates active check failed when connecting through certain proxy servers, reporting:

Proxy CONNECT failed: HTTP/1.0 200 connected

This happened because check-cert only accepted HTTP/1.1 responses from the proxy during tunnel establishment. Some proxies respond with HTTP/1.0, which is equally valid. The check now accepts both HTTP/1.0 and HTTP/1.1 success responses from proxy servers configured via the proxy option in the check settings.

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