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Artifact poisoning vulnerability in action-download-artifact v5 and earlier

High severity GitHub Reviewed Published Nov 24, 2024 in dawidd6/action-download-artifact • Updated Nov 25, 2024

Package

actions dawidd6/action-download-artifact (GitHub Actions)

Affected versions

< 6

Patched versions

6

Description

Summary

In versions of dawidd6/action-download-artifact before v6, a repository's forks were also searched by default when attempting to find matching artifacts. This could be exploited by an unprivileged attacker to introduce compromised artifacts (such as malicious executables) into a privileged workflow context, as creating a fork requires no privileges.

Users should immediately upgrade to v6 or newer, which changes the default behavior to avoid searching forks for matching artifacts. Users who cannot upgrade should explicitly set allow_forks: false to disable searching forks for artifacts.

Details

GitHub's artifact storage for workflows does not natively distinguish between artifacts created by a repository and artifacts created by forks of that repository. As a result, attempting to retrieve the "latest" artifact for a workflow run can return artifacts produced by a fork, rather than its upstream.

Because any GitHub user can create a fork of a public repository, this allows for artifact poisoning in the following scenarios (as well as potentially others):

  1. Repository alice/foo runs build.yml, producing build.exe
  2. Repository alice/foo runs publish.yml, which uses action-download-artifact@v5 to retrieve the latest build.exe from build.yml

To compromise publish.yml in this scenario, Mallory forks alice/foo to mallory/foo, and then modifies build.yml to produce a compromised build.exe. Mallory can then repeatedly trigger their copy of build.yml to ensure that their compromised build.exe is always the latest artifact, meaning that Alice's publish.yml will retrieve it.

Additional details on this vulnerability can be found in this blog post from 2022:

Impact

This vulnerability impacts all repositories on GitHub that use action-download-artifacts@v5 or older and do not disable allow_forks: true, which is the default.

If a repository is affected, the severity ranges from downstream contamination (such as publishing attacker-controlled artifacts) to direct workflow compromise (if the retrieved artifact is then executed in a privileged workflow context, such as push or pull_request_target).

References

@dawidd6 dawidd6 published to dawidd6/action-download-artifact Nov 24, 2024
Published to the GitHub Advisory Database Nov 25, 2024
Reviewed Nov 25, 2024
Last updated Nov 25, 2024

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

Weaknesses

CVE ID

No known CVE

GHSA ID

GHSA-5xr6-xhww-33m4

Source code

Credits

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