# CVE-2026-50013: Hoverfly: Process Crash via Concurrent Map Write Race Condition in Diff Mode

> An attacker can crash the Hoverfly API simulation tool by sending concurrent requests while it is running in Diff mode.

- **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:** 11 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-qrh4-p6v4-mrfg, GO-2026-5977

## What is CVE-2026-50013?

CVE-2026-50013 is a high-severity vulnerability in SpectoLabs hoverfly, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Hoverfly is an open source API simulation tool. Prior to version 1.12.8, when Hoverfly is running in Diff mode, the `AddDiff()` function writes to the shared `responsesDiff` map without any synchronization (no mutex). When multiple proxy requests are processed concurrently (the normal case for any proxy), the concurrent map writes trigger Go's built-in race detector which causes a `fatal error: concurrent map read and map write`, immediately killing the entire Hoverfly process. This is trivially exploitable by sending multiple simultaneous requests. Version 1.12.8 patches the issue.

Weakness: CWE-820 (Missing Synchronization), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-50013?

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-2026-50013?

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

## Is CVE-2026-50013 being exploited?

There is no known exploitation of CVE-2026-50013 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-50013 and fix it if it is affected.

What it is: CVE-2026-50013 is a high-severity vulnerability in SpectoLabs hoverfly, published on 11 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-2026-50013 in the wild and no public exploit code.

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-2026-50013/ (Markdown: https://insights.sbomify.com/CVE-2026-50013/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-50013
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-50013
- OSV: https://osv.dev/vulnerability/CVE-2026-50013

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-50013/
Summaries are generated and may contain mistakes; the official description above is the record.