Harden-Runner is a CI/CD security agent that works like an EDR for GitHub Actions runners. In versions 2.15.1 and below, a DNS over HTTPS (DoH) vulnerability allows attackers to bypass egress-policy: block network restrictions by tunneling exfiltrated data through permitted HTTPS endpoints like dns.google. The attack works by encoding sensitive data (e.g., the runner's hostname) as subdomains in DoH queries, which appear as legitimate HTTPS traffic to Harden-Runner's domain-based filtering but are ultimately forwarded to an attacker-controlled domain. This effectively enables data exfiltration without directly connecting to any blocked destination. Exploitation requires the attacker to already have code execution within the GitHub Actions workflow. The issue was fixed in version 2.16.0.
History

Tue, 24 Mar 2026 12:45:00 +0000

Type Values Removed Values Added
First Time appeared Stepsecurity
Stepsecurity harden-runner
CPEs cpe:2.3:a:stepsecurity:harden-runner:*:*:*:*:community:*:*:*
Vendors & Products Stepsecurity
Stepsecurity harden-runner

Sat, 21 Mar 2026 05:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-807
References
Metrics threat_severity

None

cvssV3_1

{'score': 4.9, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N'}

threat_severity

Moderate


Fri, 20 Mar 2026 16:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 20 Mar 2026 09:00:00 +0000

Type Values Removed Values Added
First Time appeared Step Security
Step Security harden Runner
Vendors & Products Step Security
Step Security harden Runner

Fri, 20 Mar 2026 04:45:00 +0000

Type Values Removed Values Added
Description Harden-Runner is a CI/CD security agent that works like an EDR for GitHub Actions runners. In versions 2.15.1 and below, a DNS over HTTPS (DoH) vulnerability allows attackers to bypass egress-policy: block network restrictions by tunneling exfiltrated data through permitted HTTPS endpoints like dns.google. The attack works by encoding sensitive data (e.g., the runner's hostname) as subdomains in DoH queries, which appear as legitimate HTTPS traffic to Harden-Runner's domain-based filtering but are ultimately forwarded to an attacker-controlled domain. This effectively enables data exfiltration without directly connecting to any blocked destination. Exploitation requires the attacker to already have code execution within the GitHub Actions workflow. The issue was fixed in version 2.16.0.
Title Egress Policy Bypass via DNS over HTTPS (DoH) in Harden-Runner (Community Tier)
Weaknesses CWE-693
CWE-863
References
Metrics cvssV4_0

{'score': 4.6, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-20T16:05:57.731Z

Reserved: 2026-03-17T00:05:53.284Z

Link: CVE-2026-32947

cve-icon Vulnrichment

Updated: 2026-03-20T16:05:52.816Z

cve-icon NVD

Status : Analyzed

Published: 2026-03-20T05:16:13.923

Modified: 2026-03-24T12:33:33.540

Link: CVE-2026-32947

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-03-20T04:03:03Z

Links: CVE-2026-32947 - Bugzilla