CVE-2024-40636 is a low-severity (CVSS 2.5) CWE-532 vulnerability in Steeltoe.Discovery.Eureka. A fix is available for Steeltoe.Discovery.Eureka — see the affected versions and patch details below.
Steeltoe Leaks Basic Auth Credentials to Logs After Fetch Registry Error
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-40636.
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
Steeltoe.Discovery.Eureka.NETSteeltoe.Discovery.EurekaBase.NETSteeltoe.Discovery.ClientCore.NETSteeltoe.Discovery.ClientAutofacReal-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
When utilizing multiple Eureka server service URLs with basic auth and encountering an issue with fetching the service registry, an error is logged with the Eureka server service URLs but only the first URL is masked.
Details
Package: Steeltoe.Discovery.Eureka
Package version: 3.2.1
Branch: "release/3.2"
File name: DiscoveryClient.cs
Line number: 325
Code in question: _logger.LogError(e, "FetchRegistry Failed for Eureka service urls: {EurekaServerServiceUrls}", new Uri(ClientConfig.EurekaServerServiceUrls).ToMaskedString());
Error message in logs: FetchRegistry Failed for Eureka service urls: https://****:****@eureka1.com:443/eureka,https://user:[email protected]:443/eureka
I thought new Uri(clientOptions.EurekaServerServiceUrls) would throw a UriFormatException since there are multiple URLs but my logs are showing two URLs regardless.
PoC
- Set Eureka config with multiple server URLs with basic auth
- Apologies for not being more descriptive for this step, but I believe we would just need to trigger an exception in
FetchFullRegistryAsync. - Check the logs and should see the error
Impact
Vulnerability: Credential leakage in the logs Who does it impact?: Users who are using peer awareness with Spring Eureka
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Steeltoe.Discovery.Eureka | all versions | 3.2.8dotnet add package Steeltoe.Discovery.Eureka --version 3.2.8 |
| .NETNuGet | Steeltoe.Discovery.EurekaBase | all versions | No fix |
| .NETNuGet | Steeltoe.Discovery.ClientCore | all versions | No fix |
| .NETNuGet | Steeltoe.Discovery.ClientAutofac | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Steeltoe.Discovery.Eureka, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Steeltoe.Discovery.Eureka to 3.2.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-40636 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2024-40636 in your dependencies?
Find it across NuGet, including transitive dependencies.