CVE-2023-30521

Vulnerability

Description

The Jenkins Assembla merge request builder Plugin, in versions 1.1.13 and earlier, contains a missing permission check in a function that triggers builds. According to the official Jenkins security advisory, this flaw allows unauthenticated attackers to trigger builds of jobs corresponding to an attacker-specified repository [1][3]. The vulnerability stems from the plugin failing to verify that the requesting user has the necessary permissions to initiate a build, effectively exposing functionality that should be restricted.

Attack

Vector and Prerequisites

An attacker can exploit this vulnerability without needing any authentication or prior access to the Jenkins instance. The only requirement is the ability to send crafted requests to the Jenkins server. The attacker can specify any repository they choose, which means they can trigger builds for jobs associated with that repository, potentially causing Jenkins to execute builds based on arbitrary or malicious inputs [2].

Impact

By triggering builds at will, an unauthenticated attacker can consume Jenkins build resources unexpectedly, leading to denial of service or resource exhaustion. Moreover, if the attacker can control the build configuration or parameters, they might inject malicious code or cause builds to fail in ways that disrupt operations. In some Jenkins configurations, triggered builds might also have access to sensitive credentials or systems, escalating the potential damage beyond simple resource abuse.

Mitigation and

Status

As of the Jenkins security advisory published on April 12, 2023, no fix is listed for this plugin; it remains among the plugins with unresolved security issues [1][2]. Users are advised to disable the plugin if it is not needed, restrict network access to the Jenkins instance, or implement a reverse proxy with authentication to block unauthenticated requests. The vulnerability is identified as CVE-2023-30521 and carries no CVSS score from NVD at this time, though the advisory does not assign a severity score [1][3].