# CVE-2026-50013: SpectoLabs Hoverfly race condition in Diff mode

Source: https://junglewise.ai/threats/cve-2026-50013-spectolabs-hoverfly-race-condition-in-diff-mode  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-11. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-50013 · Severity: high · CVSS 7.5 · Published 2026-09-11

Hoverfly is an API simulation tool used for development and testing. A flaw in its 'Diff' mode allows an attacker to crash the service by sending multiple simultaneous requests. This results in a total service outage, disrupting testing workflows and requiring a manual restart of the application.

Technologies: [github.com/SpectoLabs/hoverfly (Go)](https://junglewise.ai/threats/technologies/github-com-spectolabs-hoverfly). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-50013 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-50013 being exploited in the wild.

**How severe is CVE-2026-50013?** High severity, with a CVSS score of 7.5, published 11 September 2026.

**Which products and versions are affected?** github.com/SpectoLabs/hoverfly (Go) <= 1.12.7, SEMVER:introduced=0,fixed=1.12.8; SpectoLabs Hoverfly <= 1.12.7.

**Is there a fix for CVE-2026-50013?** Yes. github.com/SpectoLabs/hoverfly (Go): upgrade to 1.12.8 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-50013 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-50013?** Check whether you run github.com/SpectoLabs/hoverfly (Go) or SpectoLabs Hoverfly at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/SpectoLabs/hoverfly (Go): upgrade to 1.12.8 or later

  ```sh
  go get github.com/SpectoLabs/hoverfly@v1.12.8
  ```


## Technical details

A race condition exists in the `AddDiff()` function within `core/hoverfly_service.go`. When Hoverfly is configured in 'Diff' mode, it attempts to write to the shared `responsesDiff` map without proper synchronization (mutex locking). Because Go's `net/http` server handles requests concurrently in separate goroutines, simultaneous requests trigger Go's built-in runtime race detector. This results in an unrecoverable 'fatal error: concurrent map read and map write', which immediately terminates the process. The vulnerability is fixed in version 1.12.8.

## Affected products

- SpectoLabs hoverfly <= 1.12.7

## Identifiers

- CVE-2026-50013
- GHSA-qrh4-p6v4-mrfg
- GO-2026-5977

## Timeline

- 2026-06-03: patched: Version 1.12.8 released
- 2026-07-14: disclosed: GitHub Advisory published

## References

- [https://api.github.com/users/Kr1shna4garwal](https://api.github.com/users/Kr1shna4garwal)
- [https://github.com/Kr1shna4garwal](https://github.com/Kr1shna4garwal)
- [https://api.github.com/users/Kr1shna4garwal/gists%7B/gist_id%7D](https://api.github.com/users/Kr1shna4garwal/gists%7B/gist_id%7D)
- [https://api.github.com/users/Kr1shna4garwal/repos](https://api.github.com/users/Kr1shna4garwal/repos)
- [https://avatars.githubusercontent.com/u/85845881?v=4](https://avatars.githubusercontent.com/u/85845881?v=4)
- [https://api.github.com/users/Kr1shna4garwal/events%7B/privacy%7D](https://api.github.com/users/Kr1shna4garwal/events%7B/privacy%7D)

## Related threats

- [SpectoLabs Hoverfly denial of service via goroutine leak in post-serve actions](https://junglewise.ai/threats/cve-2026-50018-spectolabs-hoverfly-denial-of-service-via-goroutine-leak-in-post)
- [WebSocket endpoint `/api/v2/ws/logs` reachable without authentication even when --auth is enabled](https://junglewise.ai/threats/cve-2025-54376-websocket-endpoint-api-v2-ws-logs-reachable-without)
- [Hoverfly is vulnerable to Remote Code Execution through an insecure middleware implementation](https://junglewise.ai/threats/cve-2025-54123-hoverfly-is-vulnerable-to-remote-code-execution-through-an)
- [Hoverfly allows an arbitrary file read in the `/api/v2/simulation` endpoint (`GHSL-2023-274`)](https://junglewise.ai/threats/cve-2024-45388-hoverfly-allows-an-arbitrary-file-read-in-the-api-v2-simulation)