Auth bypass in Step-Security Harden-Runner
CVE-2026-32946
Harden-Runner is a CI/CD security agent that works like an EDR for GitHub Actions runners. In versions 2.15.1 and below, the Harden-Runner that allows bypass of the egress-policy: block network restriction using DNS queries over TCP. Egress policies are enforced on GitHub runners by filtering outbound connections at the network layer. When egress-policy: block is enabled with a restrictive allowed-endpoints list (e.g., only github.com:443), all non-compliant traffic should be denied. However, DNS queries over TCP, commonly used for large responses or fallback from UDP, are not adequately restricted. Tools like dig can explicitly initiate TCP-based DNS queries (+tcp flag) without being blocked. This vulnerability requires the attacker to already have code execution capabilities within the GitHub Actions workflow. The issue has been fixed in version 2.16.0.
EPSS: 0.003 (16.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 2.7 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N.
Affected products
- Step-security Harden-runner — versions < 2.16.0
- Stepsecurity Harden-runner
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-32946?
- CVE-2026-32946 is a low-severity vulnerability in Step-Security Harden-Runner, classified under Protection Mechanism Failure. CVSS score: 2.7/10. Published 2026-03-20.
- How severe is CVE-2026-32946?
- Low severity. CVSS v3 base score is 2.7 out of 10.