Summary
Steeltoe.Discovery.Eureka: malformed enum/bool/timestamp field aborts entire registry fetch (DoS)
Steeltoe's Eureka discovery client deserializes the registry response as a single unit. If any registered instance contains a field value that cannot be parsed (for example, an unrecognized actionType, a non-boolean value for isCoordinatingDiscoveryServer, or a non-numeric timestamp), deserialization of the entire registry fails. All Steeltoe Eureka clients connected to that registry then receive an empty or stale instance list until the malformed registration is removed.
This is a related but distinct issue from CVE-2026-50196, which addressed only the DataCenterInfo.name field.
Affected configuration
- Application uses
EurekaDiscoveryClient(any deployment, including self-hosted Eureka). - The registry contains at least one service instance with an unrecognized value in a field such as
actionType,status,isCoordinatingDiscoveryServer, or timestamp fields. - Mixed-platform environments, for example, Java or Spring services co-existing in the same Eureka registry, are more likely to encounter this condition.
Mitigations
If an immediate upgrade is not possible:
- Audit the Eureka registry for registrations containing non-standard field values, particularly those originating from non-.NET clients.
- Restrict write access to the Eureka registration API to trusted services.
Impact
Any principal that can register or update a service instance in the Eureka registry can trigger a service-discovery outage for all Steeltoe applications connected to the same registry. The outage persists until the offending registration is removed.
CVE-2026-81515 has a CVSS score of 7.5 (High). 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 (4.3.0); 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.
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Frequently Asked Questions
- What is CVE-2026-81515? CVE-2026-81515 is a high-severity security vulnerability in Steeltoe.Discovery.Eureka (nuget), affecting versions >= 4.0.0, <= 4.2.0. It is fixed in 4.3.0.
- How severe is CVE-2026-81515? CVE-2026-81515 has a CVSS score of 7.5 (High). 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 Steeltoe.Discovery.Eureka are affected by CVE-2026-81515? Steeltoe.Discovery.Eureka (nuget) versions >= 4.0.0, <= 4.2.0 is affected.
- Is there a fix for CVE-2026-81515? Yes. CVE-2026-81515 is fixed in 4.3.0. Upgrade to this version or later.
- Is CVE-2026-81515 exploitable, and should I be worried? Whether CVE-2026-81515 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-2026-81515 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-2026-81515? Upgrade
Steeltoe.Discovery.Eurekato 4.3.0 or later.