Vulnerability · Published Sep 11, 2026 · Assigned by GitHub_M
CVE-2026-50013Hoverfly: Process Crash via Concurrent Map Write Race Condition in Diff Mode
High 7.5
In plain English
A high-severity race condition in hoverfly from SpectoLabs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/SpectoLabs/hoverfly | 1.12.8 | GHSA-qrh4-p6v4-mrfg |
| Go | github.com/SpectoLabs/hoverfly | 1.12.8 | GO-2026-5977 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| SpectoLabs | hoverfly | < 1.12.8 |
Weakness: CWE-362, CWE-820 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/SpectoLabs/hoverfly/security/advisories/GHSA-qrh4-p6v4-mrfg x_refsource_CONFIRM
- https://github.com/SpectoLabs/hoverfly/pull/1227 x_refsource_MISC
- https://github.com/SpectoLabs/hoverfly/releases/tag/v1.12.8 x_refsource_MISC