Cortex v1.21.1

Version 1.21.1 is a critical stability and security release focused on hardening Cortex against resource exhaustion attacks and multi-tenant bypasses. It resolves multiple panic conditions in the distributor and gRPC clients while introducing stricter validation for native histograms and incoming network packets.

Comprehensive Security Hardening against DoS and Multi-tenant Vulnerabilities — This release closes several critical attack vectors, including memory exhaustion (OOM) via malicious histograms or gzip payloads, connection flooding in the gossip network, and unauthorized cross-tenant data pushes. Deploying this is essential for maintaining a secure multi-tenant environment.

Prevention of Service Panics in gRPC and Distributor Paths — Users using Snappy compression for gRPC or encountering high-load scenarios during distributor timeouts will no longer experience intermittent service crashes, leading to improved uptime for ingestion and querying.

Credential Masking for Storage and Authentication Configs — Operators can now safely share the output of the /config endpoint for troubleshooting without the risk of leaking sensitive credentials for storage backends like Swift, Redis, or etcd.