CVE-2026-40891 OpenTelemetry dotnet: Unbounded `grpc-status-details-bin` parsing in OTLP/gRPC retry handling
A malicious gRPC server can cause excessive memory allocation and denial of service in OpenTelemetry dotnet exporters via malformed status details.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40891?
CVE-2026-40891 is a medium-severity denial of service vulnerability in open-telemetry OpenTelemetry.Exporter.OpenTelemetryProtocol, published on 23 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
OpenTelemetry dotnet is a dotnet telemetry framework. From 1.13.1 to before 1.15.2, When exporting telemetry over gRPC using the OpenTelemetry Protocol (OTLP), the exporter may parse a server-provided grpc-status-details-bin trailer during retry handling. Prior to the fix, a malformed trailer could encode an extremely large length-delimited protobuf field which was used directly for allocation, allowing excessive memory allocation and potential denial of service (DoS). This vulnerability is fixed in 1.15.2.
Weakness: CWE-789
Which versions are affected by CVE-2026-40891?
2 open source packages ship an affected version, including OpenTelemetry.Exporter.OpenTelemetryProtocol. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
OpenTelemetry.Exporter.OpenTelemetryProtocol NuGet | From 1.13.1 | 1.15.3 |
OpenTelemetry.Exporter.OpenTelemetryProtocol NuGet | From 1.13.1 | 1.15.3 |
Products include Opentelemetry Opentelemetry.
How do I fix CVE-2026-40891?
Upgrade OpenTelemetry.Exporter.OpenTelemetryProtocol to 1.15.3 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-40891 being exploited?
There is no known exploitation of CVE-2026-40891 in the wild and no public exploit code.
Other vulnerabilities in open-telemetry OpenTelemetry.Exporter.OpenTelemetryProtocol
- CVE-2026-29181 OpenTelemetry-Go multi-value `baggage` header extraction causes excessive allocations (remote dos amplification)
- CVE-2023-47108 DoS vulnerability in otelgrpc (uncontrolled resource consumption) due to unbound cardinality metrics
- CVE-2023-45142 OpenTelemetry-Go Contrib has DoS vulnerability in otelhttp due to unbound cardinality metrics
- CVE-2023-43810 opentelemetry-instrumentation Denial of Service vulnerability due to unbound cardinality metrics
- CVE-2026-39883 opentelemetry-go: BSD kenv command not using absolute path enables PATH hijacking
Sources
Also known as GHSA-mr8r-92fq-pj8p, MINI-6xp2-q72v-66r9.