GHSA-67c9-f6v2-qv86 Steeltoe.Discovery.Consul: malformed 'secure' metadata aborts service instance lookup (DoS)

• NuGet Steeltoe.Discovery.Consul: >= 4.0.0, < 4.3.0 → fixed in 4.3.0

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, 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 non-standard `secure` metadata values. • Restrict write access to the Consul service registration API to trusted services.