CVE-2026-50013

Hoverfly: Process Crash via Concurrent Map Write Race Condition in Diff Mode

Published Sep 11, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

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.

Analysis

Technical impact

Hoverfly is an open source API simulation tool. Prior to version 1.12.8, when Hoverfly is running in Diff writes to the shared responsesDiff map without any synchronization (no mutex). When multiple proxy requests are processed concurrently—the normal case for any proxy—concurrent map writes trigger Go's built-in race detector read and map write, and immediately killing the entire Hoverfly process. This flaw is trivially exploitable by sending multiple simultaneous requests, leading to a predictable crash. The issue was patched in version 1.12.8. This reflects a CWE‑362 and CWE‑820 weakness.

Affected Systems

SpectoLabs Hoverfly prior to v1.12.8, when running in Diff mode and processing concurrent traffic. Version 1.12.8 onward contains the fix.

Risk and Exploitability

The CVSS score of 7.5 indicates a high impact and requires prompt mitigation. The EPSS score is < 1% and the vulnerability is not listed in CISA KEV does not require special privileges: an mode via network traffic to the Hoverfly proxy, and the vulnerability is trivially exploitable by standard HTTP request tools. This corresponds to CWE‑362 and CWE‑820 weaknesses.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

SpectoLabs

hoverfly

affected

Version	Status	Constraints
`< 1.12.8`	affected	—

No data.

Vendor Product Versions

Spectolabs

Hoverfly

Version	Status	Scheme	Platform
`[0,1.12.8)`	affected	semver	—

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade Hoverfly to version 1.12.8 or later. The patch corrects the concurrent map write flaw (CWE‑362) and improper locking (CWE‑820).
If an immediate upgrade is not possible, disable Diff mode to eliminate exposure to the race condition caused by CWE‑362/CWE‑820 until the patch can be applied.
Implement automated monitoring and process restarts, such as using a container orchestration restart policy or a process supervisor, to reduce downtime if the process crashes.

Generated by OpenCVE AI on September 15, 2026 at 20:33 UTC.

Tracking

Advisories

Source	ID	Title
Github GHSA	GHSA-qrh4-p6v4-mrfg	Hoverfly: Process Crash via Concurrent Map Write Race Condition in Diff Mode

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.470% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact partial

References

Link	Providers
https://github.com/SpectoLabs/hoverfly/pull/1227
https://github.com/SpectoLabs/hoverfly/releases/tag/v1.12.8
https://github.com/SpectoLabs/hoverfly/security/advisories/GHSA-qrh4-p6v4-mrfg

History

Sep 14, 2026 9:00 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Sep 12, 2026 6:45 PM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Spectolabs Spectolabs hoverfly
Vendors & Products		Spectolabs Spectolabs hoverfly

Sep 11, 2026 11:45 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
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.
Title		Hoverfly: Process Crash via Concurrent Map Write Race Condition in Diff Mode
Weaknesses		CWE-362 CWE-820
References		https://github.com/SpectoLabs/hoverfly/pull/1227 https://github.com/SpectoLabs/hoverfly/releases/tag/v1.12.8 https://github.com/SpectoLabs/hoverfly/security/advisories/GHSA-qrh4-p6v4-mrfg
Metrics		cvssV3_1 `{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}`