High severity · published Sep 11, 2026
CVE-2026-50013
Hoverfly: Process Crash via Concurrent Map Write Race Condition in Diff Mode
7.5
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 41% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HO
hoverfly · SpectoLabs
< 1.12.8 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-50013
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-50013
github.com
https://github.com/SpectoLabs/hoverfly/pull/1227
github.com
https://github.com/SpectoLabs/hoverfly/releases/tag/v1.12.8
github.com
https://github.com/SpectoLabs/hoverfly/security/advisories/GHSA-qrh4-p6v4-mrfg
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