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.

Affected: NuGet: Steeltoe.Discovery.Consul

## Summary

Steeltoe's Consul discovery client parses the `secure` metadata field on each registered service instance using `bool.Parse`, which throws on any value other than `true` or `false`. A single service instance registered with a malformed `secure` value (for example `yes` or `1`) aborts construction of the entire instance list for that service, making the service undiscoverable. When `GetAllInstancesAsync` is used, one malformed instance in any service can abort enumeration across all services. This is the same "one malformed field aborts the whole batch" availability class as [CVE-2026-50196](https://github.com/advisories/GHSA-j8ph-6fxj-g533), but affecting the Consul discovery client.

## Impact

Any principal that can register a service in the Consul catalog can trigger a service-discovery outage for all Steeltoe applications resolving that service. The outage affects all instances of the targeted service — not just the malformed one — and persists until the offending registration is removed.

## Affected configuration

- Application uses `ConsulDiscoveryClient` (any deployment). - The Consul catalog contains at least one service instance with a `secure` metadata value that is not `true` or `false`. - Mixed-platform environments where non-.NET clients register services with non-standard metadata values are more likely to encounter this condition.

## Mitigations

If an immediate upgrade is not possible:

- Audit the Consul catalog for service registrations with n…