Traefik has released v2.11.55, a patch update for the v2.11 branch, focusing on stability and correctness in edge cases. This release addresses two specific issues that could impact production deployments, particularly those using proxy protocol or manipulating headers. For teams still on v2.11, this update is a low-risk way to keep the edge router resilient without jumping to v3.
Key Changes in v2.11.55
Proxy protocol with retries: Fixed a bug where
proxyProtocolcould panic or misbehave when the connection required retries after a partial read. The fix ensures the proxy protocol parser handlesio.ErrUnexpectedEOFgracefully, preventing crashes under flaky network conditions.Header deduplication in
stripPrefix: Corrected an issue in thestripPrefixmiddleware where theX-Forwarded-Prefixheader was duplicated when the prefix appeared multiple times. The middleware now replaces all occurrences of the exact prefix, aligning the behavior with thestripPrefixRegexmiddleware.Minor dependency updates: Bumped several transitive dependencies to patch known CVEs, reinforcing the security posture of the release.
What This Means for Developers
If you rely on the proxy protocol (e.g., for real IP preservation behind a load balancer), the retry fix eliminates a rare but critical crash scenario, especially in unstable networks. For APIs behind stripPrefix, the header dedup fix ensures clients receive a single, unambiguous X-Forwarded-Prefix value, which is critical for correct URL generation in downstream apps.
The release is fully backward-compatible; no configuration changes are required. Upgrade via the official Docker image traefik:v2.11.55 or the binary from GitHub. If you've postponed a v2.11 maintenance update, this is a solid stopgap before planning a migration to v3, which offers long-term support.
Source: https://github.com/traefik/traefik/releases/tag/v2.11.55