OpenTelemetry.Sampler.AWS & OpenTelemetry.Resources.AWS have unbounded HTTP response body readsGHSA-28xm-prxc-5866
MEDIUMFix: open-telemetry/opentelemetry-dotnet-contrib#4100GHSA-28xm-prxc-5866 is a medium-severity (CVSS 5.9) CWE-770 vulnerability in OpenTelemetry.Sampler.AWS. A fix is available for OpenTelemetry.Sampler.AWS — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-28xm-prxc-5866.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
OpenTelemetry.Sampler.AWS.NETOpenTelemetry.Resources.AWSReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Impact
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.
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.
Patches
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.
Workarounds
- Ensure the X-Ray sampling endpoint (
http://localhost:2000by 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | OpenTelemetry.Sampler.AWS | all versions | 0.1.0-alpha.8dotnet add package OpenTelemetry.Sampler.AWS --version 0.1.0-alpha.8 |
| .NETNuGet | OpenTelemetry.Resources.AWS | all versions | 1.15.1dotnet add package OpenTelemetry.Resources.AWS --version 1.15.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for OpenTelemetry.Sampler.AWS, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update OpenTelemetry.Sampler.AWS to 0.1.0-alpha.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-28xm-prxc-5866 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is GHSA-28xm-prxc-5866 in your dependencies?
Find it across NuGet, including transitive dependencies.