NextCloud Cookbook CI Workflow Command Injection via Untrusted head

NextCloud Cookbook's pull-checks.yml workflow is vulnerable to OS Command Injection
NextCloud Cookbook is a recipe library app. Prior to commit a46d9855 on the `master` branch and commit 489bb744 on the `main-0.9.x` branch, the `pull-checks.yml` workflow is vulnerable to command injection attacks because of using an untrusted `github.head_ref` field. The `github.head_ref` value is an attacker-controlled value. Assigning the value to `zzz";echo${IFS}"hello";#` can lead to command injection. Since the permission is not restricted, the attacker has a write-access to the repository. This issue is fixed in commit a46d9855 on the `master` branch and commit 489bb744 on the `main-0.9.x` branch. There is no risk for the user of the app within the NextCloud server. This only affects the main repository and possible forks of it. Those who have forked the NextCloud Cookbook repository should make sure their forks are on the latest version to prevent code injection attacks and similar.

Vulnerability Analysis

CVE-2023-31128 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. Public availability of a proof of concept (POC) exploit exists for CVE-2023-31128. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, a high impact on integrity and availability.

Attack Vector:

NETWORK

Attack Complexity:

LOW

Privileges Required:

LOW

User Interaction:

NONE

Scope:

UNCHANGED

Confidentiality Impact:

NONE

Integrity Impact:

HIGH

Availability Impact:

HIGH

Weakness Type

What is a Shell injection Vulnerability?

The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

CVE-2023-31128 has been classified to as a Shell injection vulnerability or weakness.

Products Associated with CVE-2023-31128

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Affected Versions

Exploit Probability

EPSS

1.39%

Percentile

80.20%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.