Summary
OpenTelemetry dotnet: OTLP exporter reads unbounded HTTP response bodies
Full technical description
When exporting telemetry to a back-end/collector over gRPC or HTTP using OpenTelemetry Protocol format (OTLP), if the request results in a unsuccessful request (i.e. HTTP 4xx or 5xx), the response is read into memory with no upper-bound on the number of bytes consumed.
This could cause memory exhaustion in the consuming application if the configured back-end/collector endpoint is attacker-controlled (or a network attacker can MitM the connection) and an extremely large body is returned by the response.
Details
https://github.com/open-telemetry/opentelemetry-dotnet/pull/6564 introduced a change to read the response body when a non-200 HTTP status code is received when exporting telemetry to aid debugging by operators so that the error response is included in the logs emitted by the exporter for both gRPC and HTTP/protobuf.
An unintended consequence of this change is that the response body is fully read into memory when received with no upper-bound.
This vulnerability was surfaced during the investigation of GHSA-w8rr-5gcm-pp58.
Mitigation
The application's configured back-end/collector endpoint needs to behave maliciously. If the collector/back-end is a well-behaved implementation response bodies should not be excessively large if a request error occurs.
Workarounds
None known.
Impact
If an application using the OTLP exporter is configured to use a back-end/collector endpoint that is attacker-controlled (or a network attacker can MitM the connection) and an extremely large body is returned by the response the application could have its memory exhausted and create a denial-of-service condition.
CVE-2026-40182 has a CVSS score of 5.3 (Medium). The vector is reachable from an adjacent network, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.15.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
#7017 updates the OTLP exporter for both gRPC and HTTP to:
- Limit the number of bytes read from the response body in an error condition to 4MiB (see https://github.com/open-telemetry/opentelemetry-proto/pull/781);
- Only attempt to read the response body if OpenTelemetry error logging is enabled.
Frequently Asked Questions
- What is CVE-2026-40182? CVE-2026-40182 is a medium-severity security vulnerability in OpenTelemetry.Exporter.OpenTelemetryProtocol (nuget), affecting versions >= 1.13.1, < 1.15.2. It is fixed in 1.15.2.
- How severe is CVE-2026-40182? CVE-2026-40182 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of OpenTelemetry.Exporter.OpenTelemetryProtocol are affected by CVE-2026-40182? OpenTelemetry.Exporter.OpenTelemetryProtocol (nuget) versions >= 1.13.1, < 1.15.2 is affected.
- Is there a fix for CVE-2026-40182? Yes. CVE-2026-40182 is fixed in 1.15.2. Upgrade to this version or later.
- Is CVE-2026-40182 exploitable, and should I be worried? Whether CVE-2026-40182 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-40182 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-40182? Upgrade
OpenTelemetry.Exporter.OpenTelemetryProtocolto 1.15.2 or later.