CVE-2026-40891

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.

CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-789 CWE-789

Affected Products

Vendor	Product	Versions
opentelemetry	opentelemetry	1.13.1 — 1.15.3

References

Advisories & Patches

https://github.com/open-telemetry/opentelemetry-dotnet/pull/5980 https://github.com/open-telemetry/opentelemetry-dotnet/pull/7064 https://github.com/open-telemetry/opentelemetry-dotnet/security/advisories/GHSA-mr8r-92fq-pj8p

Frequently Asked Questions

What is CVE-2026-40891? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-40891? +

CVE-2026-40891 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-40891? +

CVE-2026-40891 affects products from opentelemetry, specifically: opentelemetry. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-40891? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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