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CISA Warns of Plex Vulnerability Linked to LastPass Hack

CISA has added vulnerabilities in Plex Media Server and VMware NSX-V to its Known Exploited Vulnerabilities catalog.

The US Cybersecurity and Infrastructure Security Agency (CISA) has added vulnerabilities impacting Plex and VMware products to its Known Exploited Vulnerabilities (KEV) catalog.

Tracked as CVE-2020-5741, the first is a high-severity flaw in Plex Media Server that is described as a deserialization issue that can be exploited to execute arbitrary Python code, remotely.

“This issue allowed an attacker with access to the server administrator’s Plex account to upload a malicious file via the Camera Upload feature and have the media server execute it,” Plex noted in a May 2020 advisory.

Addressed with the release of Plex Media Server 1.19.3, the vulnerability requires for the attacker to have admin access to a Plex Media Server for successful exploitation, which made it unlikely to be targeted in attacks.

However, Plex in August 2022 disclosed a data breach that likely impacted over 15 million customers, and which resulted in usernames, emails, and password data being stolen.

This essentially opened the door for the exploitation of unpatched Plex Media Server instances still impacted by CVE-2020-5741.

While CISA added the vulnerability to the KEV list without sharing details on in-the-wild exploitation, media reports suggested recently that last year’s LastPass data breach that led to the theft of user vault data might be related to a Plex bug exploited to hack a DevOps engineer’s computer.

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Plex provided the following statement to SecurityWeek:

“We take security issues very seriously, and frequently work with external parties who report issues big or small using our guidelines and bug bounty program. When vulnerabilities are reported following responsible disclosure we address them swiftly and thoroughly, and we’ve never had a critical vulnerability published for which there wasn’t already a patched version released. And when we’ve had incidents of our own, we’ve always chosen to communicate them quickly. We are not aware of any unpatched vulnerabilities, and as always, we invite people to disclose issues to us following the guidelines linked above.

We learned from LastPass that the vulnerability that was exploited is detailed here:, which was disclosed by Plex publicly back in May, 2020 (a good 2.5 years prior to the LastPass event). At the time, as noted in that post, an updated version of the Plex Media Server was made available to all (7-MAY-2020). Unfortunately, the LastPass employee never upgraded their software to activate the patch. For reference, the version that addressed this exploit was roughly 75 versions ago. Plex will provide notifications via the admin UI about updates that are available, and will also do automatic updates in many cases.”

The second vulnerability that CISA added to its KEV list last week is CVE-2021-39144, a remote code execution issue in XStream, which was recently seen being exploited in malicious attacks targeting VMware products. VMware Cloud Foundation and NSX Data Center for vSphere (NSX-V) are impacted.

“This vulnerability can affect multiple products including but not limited to VMware Cloud Foundation,” CISA notes. 

As per the Binding Operational Directive (BOD) 22-01, federal agencies are required to address these vulnerabilities until March 31. However, all organizations are encouraged to review the catalog and apply patches where necessary.

Related: Dozens of Exploited Vulnerabilities Missing From CISA ‘Must Patch’ List

Related: 557 CVEs Added to CISA’s Known Exploited Vulnerabilities Catalog in 2022

Related: Exploited Control Web Panel Flaw Added to CISA ‘Must-Patch’ List

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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