Prometheus Exporter Toolkit vulnerable to basic authentication bypass

Open Source Vulnerabilities GO-2022-1130

If an attacker has access to a Prometheus web.yml file and users' bcrypted passwords, it would be possible to bypass security via the built-in authentication cache.

Open Source Vulnerabilities GHSA-7rg2-cxvp-9p7p

### Impact Prometheus and its exporters can be secured by a web.yml file that specifies usernames and hashed passwords for basic authentication. Passwords are hashed with bcrypt, which means that even if you have access to the hash, it is very hard to find the original password back. However, a flaw in the way this mechanism was implemented in the exporter toolkit makes it possible with people who know the hashed password to authenticate against Prometheus. A request can be forged by an attacker to poison the internal cache used to cache the computation of hashes and make subsequent requests successful. This cache is used in both happy and unhappy scenarios in order to limit side channel attacks that could tell an attacker if a user is present in the file or not. ### Patches The exporter-toolkit v0.7.3 and v0.8.2 have been released to address this issue. ### Workarounds There is no workaround but attacker must have access to the hashed password, stored in disk, to bypass the authentication. ### Credit We want to thank Lei Wan reporting this security issue.

Open Source Vulnerabilities CVE-2022-46146

Prometheus Exporter Toolkit is a utility package to build exporters. Prior to versions 0.7.2 and 0.8.2, if someone has access to a Prometheus web.yml file and users' bcrypted passwords, they can bypass security by poisoning the built-in authentication cache. Versions 0.7.2 and 0.8.2 contain a fix for the issue. There is no workaround, but attacker must have access to the hashed password to use this functionality.