Bug 2449438 (CVE-2026-32946)

Summary: CVE-2026-32946 step-security/harden-runner: Harden-Runner: Egress policy bypass via DNS over TCP
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: alcohan, cmyers, dnakabaa, gparvin, jbalunas, kaycoth, lcouzens, pahickey, rhaigner
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Harden-Runner, a security agent for GitHub Actions runners. An attacker with existing code execution capabilities within a GitHub Actions workflow can bypass network egress policies, which are security measures designed to control outbound network connections. This bypass occurs by utilizing DNS queries over TCP, allowing unauthorized network communication despite restrictive egress policies.
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Description OSIDB Bzimport 2026-03-20 05:02:15 UTC 
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.