GHSA-67c9-f6v2-qv86: High severity nuget/Steeltoe.Discovery.Consul vulnerability
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
nuget/Steeltoe.Discovery.Consulto a version that resolves this vulnerability.Fixed in 4.3.0 - Compensating control
Restrict write access to the Consul service registration API to trusted services/principals, so only trusted services can register/update service instances in the Consul catalog.
- Operational
Audit the Consul catalog for service registrations whose `secure` metadata value is not exactly `true` or `false` (e.g., values like `yes` or `1`), and remove/correct the offending registration(s), since a single malformed `secure` value can abort Steeltoe `ConsulDiscoveryClient` instance-list construction and make the service undiscoverable until fixed.
Event History
Frequently Asked Questions
Who can trigger the outage?
Any principal that can register a service instance in the Consul catalog can trigger it. No access to the Steeltoe application itself is stated as necessary.
What conditions are required for an application to be affected?
The application must use ConsulDiscoveryClient, and the Consul catalog must contain a service instance whose secure metadata value is not true or false. The advisory states this can affect any deployment using that client.
What can be done if patching is not immediately possible?
Remove the offending service registration from the Consul catalog, or correct its secure metadata value to true or false. The outage persists until the malformed registration is removed.
Can one bad registration affect more than its own instance?
Yes. A malformed secure value prevents construction of the entire instance list for the targeted service, making all of that service's instances undiscoverable. Applications using GetAllInstancesAsync can have enumeration across all services aborted by one malformed instance in any service.