# CVE-2026-50018: Hoverfly: Denial of Service via Goroutine Leak in Remote Post-Serve Actions

> An attacker can cause a denial of service in Hoverfly by triggering remote post-serve actions against unresponsive endpoints, leading to goroutine leaks and memory exhaustion.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-42j2-w334-qxw7, GO-2026-5975

## What is CVE-2026-50018?

CVE-2026-50018 is a medium-severity denial of service vulnerability in SpectoLabs hoverfly, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Hoverfly is an open source API simulation tool. Prior to version 1.12.8, remote post-serve actions use `http.DefaultClient` without any timeout configuration. When the remote endpoint is unreachable or intentionally slow (accepts TCP connection but never responds), each triggered proxy request spawns a goroutine that blocks indefinitely on `http.DefaultClient.Do()`. An attacker can cause unbounded goroutine accumulation leading to memory exhaustion and process crash (OOM kill). Unlike local post-serve action execution, this requires no binary execution, only a URL pointing to a non-responsive endpoint. Version 1.12.8 patches the issue.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-50018?

3 open source packages ship an affected version, including github.com/SpectoLabs/hoverfly.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/SpectoLabs/hoverfly` | Go | All versions | 1.12.8 |
| `github.com/SpectoLabs/hoverfly` | Go | All versions | 1.12.8 |
| `github.com/SpectoLabs/hoverfly` | Go | All versions | 1.12.8 |

## How do I fix CVE-2026-50018?

Upgrade github.com/SpectoLabs/hoverfly to 1.12.8 or later.

## Is CVE-2026-50018 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-50018 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-50018 and fix it if it is affected.

What it is: CVE-2026-50018 is a medium-severity denial of service vulnerability in SpectoLabs hoverfly, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-50018 exists.

Affected packages and fixed versions:
- github.com/SpectoLabs/hoverfly (Go): affected all versions; fixed in 1.12.8
- github.com/SpectoLabs/hoverfly (Go): affected all versions; fixed in 1.12.8
- github.com/SpectoLabs/hoverfly (Go): affected all versions; fixed in 1.12.8

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-2026-50018/ (Markdown: https://insights.sbomify.com/CVE-2026-50018/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-50018
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-50018
- OSV: https://osv.dev/vulnerability/CVE-2026-50018

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-50018/
Summaries are generated and may contain mistakes; the official description above is the record.