CVE-2026-50013: Spectolabs Hoverfly

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

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 products

• Spectolabs Hoverfly: before 1.12.8 (fixed in 1.12.8)

Published 2026-09-11. Last modified 2026-09-30.