[SECURITY] CVE-2026-40542: Apache HttpClient 5.6 SCRAM-SHA-256 mutual authentication bypass

[Arturo Bernal <abernal () apache org>]

Severity: important

Affected versions:

   - Apache HttpClient 5.6

Description:
A missing critical step in authentication in Apache HttpClient 5.6 may
allow an attacker to cause the client to accept SCRAM-SHA-256
authentication without proper mutual authentication verification.


Users are recommended to upgrade to Apache HttpClient 5.6.1. which corrects
this issue.

Credit:
This issue was reported by Rasmus Moorats.


References:
https://hc.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-40542

https://github.com/apache/httpcomponents-client/commit/726eac2323d370435d8afca1e0540aa099927f18




Arturo