Pierluigi Paganini January 28, 2024

Multiple proof-of-concept (PoC) exploits for recently disclosed critical Jenkins vulnerability CVE-2024-23897 have been released.

Researchers warn that several proof-of-concept (PoC) exploits targeting the recently disclosed critical Jenkins vulnerability, CVE-2024-23897, have been made public.

Jenkins is the most popular open source automation server, it is maintained by CloudBees and the Jenkins community. The automation server supports developers build, test and deploy their applications, it has hundreds of thousands of active installations worldwide with more than 1 million users.

The maintainers of the open-source platform have addressed nine security vulnerabilities, including a critical flaw, tracked as CVE-2024-23897, that could lead to remote code execution (RCE). The vulnerability was reported by the researcher Yaniv Nizry from Sonar who wrote a detailed analysis of the issue.

Jenkins has a built-in command line interface (CLI) to access the platform from a script or shell environment. The open-source software uses the args4j library to parse CLI command arguments and options on the Jenkins controller. The parser uses a functionality that replaces the ‘@’ character followed by a file path in an argument with the content of the file (‘expandAtFiles’). This feature is enabled by default and Jenkins 2.441 and earlier, LTS 2.426.2 and earlier does not disable it.

An attacker can abuse the default character encoding of the Jenkins controller process to read arbitrary files on the controller file system.

An attacker with “Overall/Read” permission can read entire files, while an attacker without it can read the first three lines of the files depending on the CLI commands.

The maintainers pointed out that exploiting this flaw makes it possible to read binary files containing cryptographic keys used for various Jenkins features, even with some limitations.

The popular cyberesecurity researcher Florian Roth warned of a couple of weaponized PoC exploits have been released.

The researcher German Fernandez warned of a massive exploitation of the vulnerability, querying Shodan, he found more than 75000 internet-facing instances.

The availability of “PoC exploits” will cause several threat actors to start exploiting the vulnerability in attacks in the wild.

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Pierluigi Paganini

(SecurityAffairs – hacking, Jenkins)