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.
Metrics
Affected Vendors & Products
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References
History
Fri, 20 Mar 2026 09:00:00 +0000
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Step Security
Step Security harden Runner |
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Step Security
Step Security harden Runner |
Fri, 20 Mar 2026 04:45:00 +0000
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| 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 |
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| Metrics |
cvssV4_0
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MITRE
Status: PUBLISHED
Assigner: GitHub_M
Published: 2026-03-20T04:03:03.687Z
Updated: 2026-03-20T04:03:03.687Z
Reserved: 2026-03-17T00:05:53.284Z
Link: CVE-2026-32947
Vulnrichment
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NVD
Status : Awaiting Analysis
Published: 2026-03-20T05:16:13.923
Modified: 2026-03-20T13:37:50.737
Link: CVE-2026-32947
Redhat
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