Hoverfly: Denial of Service via Goroutine Leak in Remote Post-Serve Actions

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-50018: 0.54% estimated exploitation activity in the next 30 days; percentile 45.68 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary: 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. Details: 1. Remote actions executed in goroutines without timeout (core/hoverfly.go:224-228): Post-serve actions are executed in separate goroutines with no recovery wrapper. 2. HTTP client has no timeout (core/action/action.go:128-143): http.DefaultClient has zero timeout by default in Go. If the remote server: - Accepts the TCP connection but never sends a response - Establishes TLS but never completes the handshake - Uses TCP window size 0 (flow…

Published by the source

14 Jul 2026, 18:04 UTC

Last modified by the source

14 Jul 2026, 18:04 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-42j2-w334-qxw7

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# Patch Next advisory brief: CVE-2026-50018

Advisory: Hoverfly: Denial of Service via Goroutine Leak in Remote Post-Serve Actions
IDs: CVE-2026-50018, GHSA-42j2-w334-qxw7
Record: https://patchnext.com/advisories/cve-2026-50018 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/SpectoLabs/hoverfly 1.12.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/SpectoLabs/hoverfly: affected <= 1.12.7; fixed in 1.12.8

## Suggested inspection (read-only)
- Go github.com/SpectoLabs/hoverfly: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/SpectoLabs/hoverfly.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-42j2-w334-qxw7 (GitHub-reviewed advisory GHSA-42j2-w334-qxw7 lists affected ranges: Go github.com/SpectoLabs/hoverfly >=0 <=1.12.7)

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