CVE-2026-40894 OpenTelemetry dotnet: Excessive memory allocation when parsing OpenTelemetry propagation headers
Attackers can cause denial of service in applications using OpenTelemetry dotnet libraries by sending crafted propagation headers that trigger excessive memory allocation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40894?
CVE-2026-40894 is a medium-severity denial of service vulnerability in open-telemetry OpenTelemetry.Api, published on 23 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
OpenTelemetry dotnet is a dotnet telemetry framework. In OpenTelemetry.Api 0.5.0-beta.2 to 1.15.2 and OpenTelemetry.Extensions.Propagators 1.3.1 to 1.15.2, The implementation details of the baggage, B3 and Jaeger processing code in the OpenTelemetry.Api and OpenTelemetry.Extensions.Propagators NuGet packages can allocate excessive memory when parsing which could create a potential denial of service (DoS) in the consuming application. This vulnerability is fixed in 1.15.3.
Weakness: CWE-789
Which versions are affected by CVE-2026-40894?
4 open source packages ship an affected version, including OpenTelemetry.Api and OpenTelemetry.Extensions.Propagators. It affects 3 products.
| Package | Affected | Fixed in |
|---|---|---|
OpenTelemetry.Api NuGet | From 0.5.0-beta.2 | 1.15.3 |
OpenTelemetry.Api NuGet | From 0.5.0-beta.2 | 1.15.3 |
OpenTelemetry.Extensions.Propagators NuGet | From 1.3.1 | 1.15.3 |
OpenTelemetry.Extensions.Propagators NuGet | From 1.3.1 | 1.15.3 |
Products include Opentelemetry Opentelemetry, Opentelemetry Opentelemetry.api, Opentelemetry Opentelemetry.extensions.propagators.
How do I fix CVE-2026-40894?
Upgrade OpenTelemetry.Api 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-2026-40894 being exploited?
There is no known exploitation of CVE-2026-40894 in the wild and no public exploit code.
Other vulnerabilities in open-telemetry OpenTelemetry.Api
- 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-g94r-2vxg-569j, MINI-cmrr-7m33-j4jp, ROOT-APP-NUGET-CVE-2026-40894.