Executive brief
OpenTelemetry-Go is a software library used by developers to monitor and trace the performance of Go applications. A vulnerability in how the library handles 'baggage' headers—metadata passed between services—allows a remote attacker to send specially crafted, oversized headers that the system will attempt to process and log. This can lead to a denial-of-service (DoS) condition where the application's performance is degraded due to excessive CPU usage or its storage is filled with large volumes of error logs.
Technical details
A regression in OpenTelemetry-Go versions 1.41.0 and 1.43.0 removed raw-length rejection and per-member size guards during baggage header parsing. The `Parse` function in `baggage/baggage.go` now iterates over all list members using `strings.SplitSeq` and performs full tokenization and `PathUnescape` decoding on each member without early rejection of oversized inputs. Furthermore, `propagation/baggage.go` forwards these parsing errors to the global error handler, which typically defaults to logging. An unauthenticated remote attacker can exploit this by sending malformed or extremely large baggage headers, leading to CPU exhaustion and log disk space exhaustion. The issue is mitigated by transport-level header limits but remains a risk for services with high limits or default error handling.
Affected products
- OpenTelemetry opentelemetry-go (go.opentelemetry.io/otel/baggage) 1.41.0, 1.43.0
- OpenTelemetry opentelemetry-go (go.opentelemetry.io/otel/propagation) 1.41.0, 1.43.0
Timeline
- 2026-02-28: patched: Initial PR to comply with W3C limits merged
- 2026-05-28: advisory: GitHub Security Advisory published
- 2026-06-04: disclosed: CVE published to NVD