CVE-2026-41173

OpenTelemetry.Sampler.AWS reads unbounded HTTP response bodies from a configured AWS X-Ray remote sampling endpoint into memory.

OpenTelemetry.Resources.AWS reads unbounded HTTP response bodies from a configured AWS EC2/ECS/EKS remote instance metadata service endpoint into memory.

Both of these would allow an attacker-controlled endpoint or be acting as a Man-in-the-Middle (MitM) to cause excessive memory allocation and possible process termination (via Out of Memory (OOM)).

Details

OpenTelemetry.Sampler.AWS

AWSXRaySamplerClient.DoRequestAsync called HttpClient.SendAsync followed by ReadAsStringAsync(), which materializes the entire HTTP response body into a single in-memory string with no size limit. The sampling endpoint is configurable via AWSXRayRemoteSamplerBuilder.SetEndpoint (default: http://localhost:2000).

An attacker who controls the configured endpoint, or who can intercept traffic to it (MitM), can return an arbitrarily large response body. This causes unbounded heap allocation in the consuming process, leading to high transient memory pressure, garbage-collection stalls, or an OutOfMemoryException that terminates the process.

OpenTelemetry.Resources.AWS

The AWSEC2Detector, AWSECSDetector and AWSEKSDetector classes all make HTTP requests to the relevant AWS metadata service (http://169.254.169.254, ECS_CONTAINER_METADATA_URI/ECS_CONTAINER_METADATA_URI_V4 or https://kubernetes.default.svc respectively) to obtain metadata about the running process and its infrastructure.

An attacker who controls the configured endpoint(s), or who can intercept traffic to them (MiTM), can return an arbitrarily large response body. This causes unbounded heap allocation in the consuming process, leading to high transient memory pressure, garbage-collection stalls, or an OutOfMemoryException that terminates the process.

Mitigating Factors

• The default X-Ray sampling endpoint is http://localhost:2000, which limits remote exposure in default configurations.
• Risk increases materially when operators configure the sampler to point at a remote or untrusted endpoint.

Workarounds

• Ensure the X-Ray sampling endpoint (http://localhost:2000 by default) is not accessible to untrusted parties.
• Use network-level controls (firewall rules, mTLS, service mesh) to prevent Man-in-the-Middle (MitM) attacks on the sampling endpoint and/or EC2/ECS/EKS connection.
• If using a remote endpoint, place it behind a reverse proxy that enforces a response body size limit.

Denial of Service (DoS). An attacker can destabilize or crash the application by forcing unbounded memory allocation through the X-Ray sampling and/or EC2/ECS/EKS HTTP response paths.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-41173 has a CVSS score of 5.9 (Medium). The vector is network-reachable, 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 (0.1.0-alpha.8, 1.15.1); upgrading removes the vulnerable code path.

Kodem intelligence

Fixed in OpenTelemetry.Sampler.AWS version 0.1.0-alpha.8 and OpenTelemetry.Resources.AWS version 1.15.1.

The fixes (#4100, #4122) introduce changes that introduce limits to HttpClient requests so that the response body is streamed rather than buffered entirely in memory.

1. What is CVE-2026-41173? CVE-2026-41173 is a medium-severity allocation of resources without limits or throttling vulnerability in OpenTelemetry.Sampler.AWS (nuget), affecting versions < 0.1.0-alpha.8. It is fixed in 0.1.0-alpha.8, 1.15.1. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-41173? CVE-2026-41173 has a CVSS score of 5.9 (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.
3. Which packages are affected by CVE-2026-41173?
   • OpenTelemetry.Sampler.AWS (nuget) (versions < 0.1.0-alpha.8)
   • OpenTelemetry.Resources.AWS (nuget) (versions < 1.15.1)
4. Is there a fix for CVE-2026-41173? Yes. CVE-2026-41173 is fixed in 0.1.0-alpha.8, 1.15.1. Upgrade to this version or later.
5. Is CVE-2026-41173 exploitable, and should I be worried? Whether CVE-2026-41173 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
6. What actually determines whether CVE-2026-41173 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.
7. How do I fix CVE-2026-41173?
   • Upgrade OpenTelemetry.Sampler.AWS to 0.1.0-alpha.8 or later
   • Upgrade OpenTelemetry.Resources.AWS to 1.15.1 or later