Vulnerability · Published Mar 20, 2026 · Assigned by GitHub_M
CVE-2026-32947Egress Policy Bypass via DNS over HTTPS (DoH) in Harden-Runner (Community Tier)
Medium 4.6
In plain English
A medium-severity incorrect authorization in harden-runner from step-security. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities).
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| step-security | harden-runner | < 2.16 |
Weakness: CWE-693, CWE-863 · 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