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

> A malicious service registration with invalid metadata can crash the discovery client, making services undiscoverable in Steeltoe applications.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-67c9-f6v2-qv86

## What is CVE-2026-81516?

CVE-2026-81516 is a high-severity denial of service vulnerability in SteeltoeOSS security-advisories, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions)

## Which versions are affected by CVE-2026-81516?

2 open source packages ship an affected version, including Steeltoe.Discovery.Consul.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Steeltoe.Discovery.Consul` | NuGet | From 4.0.0 | 4.3.0 |
| `Steeltoe.Discovery.Consul` | NuGet | From 4.0.0 | 4.3.0 |

## How do I fix CVE-2026-81516?

Upgrade Steeltoe.Discovery.Consul to 4.3.0 or later.

## Is CVE-2026-81516 being exploited?

There is no known exploitation of CVE-2026-81516 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81516 and fix it if it is affected.

What it is: CVE-2026-81516 is a high-severity denial of service vulnerability in SteeltoeOSS security-advisories, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-81516 in the wild and no public exploit code.

Affected packages and fixed versions:
- Steeltoe.Discovery.Consul (NuGet): affected from 4.0.0; fixed in 4.3.0
- Steeltoe.Discovery.Consul (NuGet): affected from 4.0.0; fixed in 4.3.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-81516/ (Markdown: https://insights.sbomify.com/CVE-2026-81516/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81516
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81516
- OSV: https://osv.dev/vulnerability/CVE-2026-81516

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81516/
Summaries are generated and may contain mistakes; the official description above is the record.