4.6

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-32946

CVE-2026-32946: Egress Policy Bypass via DNS over TCP in Harden-Runner (Community Tier)

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.

(GitHub Advisory)

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CVE-2026-32946

CVE-2026-32946:

4.6

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
step-security/harden-runner	actions	<= 2.15.1	2.16.0

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability, an egress policy bypass via DNS over TCP, resides in the step-security/agent binary, not directly in the step-security/harden-runner GitHub Action's JavaScript code. The harden-runner action is responsible for downloading and executing this agent.

The analysis of the patch that remediates this vulnerability shows that the fix was to update the version of the agent being downloaded. The commit fa2e9d605c4eeb9fcad4c99c224cee0c6c7f3594 modifies the installAgent function in src/install-agent.ts to download agent version v0.14.4 instead of the vulnerable v0.14.3.

Therefore, the installAgent function is the critical component in the harden-runner action related to this vulnerability. It is the function responsible for provisioning the vulnerable component. During the execution of a GitHub Actions workflow using a vulnerable version of harden-runner, this function would be called, and it would install the agent that allows the egress policy bypass. A runtime profile of the action's execution would show installAgent as part of the setup process that leads to the vulnerable state.

Vulnerable functions

installAgent

src/install-agent.ts

The `installAgent` function in `src/install-agent.ts` is responsible for downloading and installing the `step-security/agent`, which contains the core logic for network traffic filtering. The vulnerability was not in the JavaScript code of `harden-runner` itself, but in the binary agent it deployed. This function was downloading and installing a vulnerable version of the agent (v0.14.3). The patch addresses the vulnerability by updating the download URL to fetch a fixed version of the agent (v0.14.4). Therefore, `installAgent` is the key function that would be observed in a runtime profile during the setup of the vulnerable environment.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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