Argo CD repo-server fails against Azure DevOps: "ssh-rsa is about to be deprecated"

Argo CD repo-server suddenly stops pulling git repositories from Azure DevOps Repos, showing: ssh-rsa is about to be deprecated and your request has been throttled. Please use rsa-sha2-256 or rsa-sha2-512 instead. Microsoft deprecated ssh-rsa host key / public key algorithms in 2024 with throttling and brownouts. Argo CD's repo-server depended on golang.org/x/crypto at v0.19.0, which does not support the rsa-sha2-256/512 signature algorithms (support landed in x/crypto v0.21.0).

Argo CD needed a newer golang.org/x/crypto to negotiate rsa-sha2-256/512 with Azure DevOps. The fix shipped in patch releases: upgrade to 2.10.9, 2.9.14, or 2.8.18 (matching your minor line) and repo-server pulls work again through the brownouts. Multiple users verified the fix against live Azure brownout windows on the issue thread. If you cannot upgrade immediately, switch the repo connection from SSH to HTTPS with a personal access token as a workaround.

Source: https://github.com/argoproj/argo-cd/issues/17634

Source: https://github.com/argoproj/argo-cd/issues/17634