Jenkins patched a critical RCE flaw in its open source automation server

Jenkins developers fixed a critical RCE vulnerability in the popular open source automation server along with many other issues.

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 more than 133,000 active installations worldwide with more than 1 million users.

The developers of the automation server recently patched several vulnerabilities, including a critical flaw that can be exploited by a remote attacker for arbitrary code execution.

A security researcher recently reported to the Beyond Security’s SecuriTeam Secure Disclosure program that the popular automation server is affected by a critical issue related to Java deserialization.

Jenkins open source automation server

The vulnerability could be exploited by a remote unauthenticated attacker to execute arbitrary code on the target system, a hacker just needs to send two specially crafted requests to the affected server.

“CLI: Unauthenticated remote code execution

SECURITY-429 / CVE-2017-1000353

An unauthenticated remote code execution vulnerability allowed attackers to transfer a serialized Java SignedObject object to the remoting-based Jenkins CLI, that would be deserialized using a new ObjectInputStream, bypassing the existing blacklist-based protection mechanism.

SignedObject has been added to the remoting blacklist.”  reads the security advisory published by Jenkins.

Jenkins developers admitted that the flaw “allowed attackers to transfer a serialized Java SignedObject object to the remoting-based Jenkins CLI, that would be deserialized using a new ObjectInputStream, bypassing the existing blacklist-based protection mechanism.”

The development team released the versions 2.57 and 2.46.2 (LTS) to address the issue. The security updates also fixed other problems, such as multiple high severity cross-site request forgery (CSRF) vulnerabilities and high severity cross-site request forgery (CSRF) vulnerabilities.

According to the development team, the CSRF flaws can be exploited by attackers to conduct several malicious activities such as restarting the server and installing plugins.

The security updates also fixed a Login command that allowed to impersonate any Jenkins user (SECURITY-466 / CVE-2017-1000354) and an XStream issue that could cause Java crash when trying to instantiate void/Void (SECURITY-503 / CVE-2017-1000355).

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