Microsoft Warns of ‘Nimbuspwn’ Security Flaws Haunting Linux

Vulnerability researchers at Microsoft are documenting the discovery of a pair of Linux privilege escalation flaws that could be chained together to plant dangerous malware or backdoors.

The vulnerabilities, collectively known as Nimbuspwn, provide a roadmap for attackers to elevate privileges to root on many Linux desktop endpoints, Redmond said in a public advisory.

Microsoft said its researchers created an experimental exploit capable of delivering a root backdoor with permanent root access.

“The vulnerabilities can be chained together to gain root privileges on Linux systems, allowing attackers to deploy payloads, like a root backdoor, and perform other malicious actions via arbitrary root code execution,” said Jonathan Bar Or, a member of the Microsoft 365 Defender Research Team.

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“The Nimbuspwn bug could potentially be leveraged as a vector for root access by more sophisticated threats, such as malware or ransomware, to achieve greater impact on vulnerable devices,” he added.

Bar Or said researchers in the Microsoft 365 Defender Research Team discovered the vulnerabilities by listening to messages on the System Bus while performing code reviews and dynamic analysis on services that run as root.

The researchers found an “odd pattern” in a systemd unit called networkd-dispatcher and stumbled onto multiple security concerns, including directory traversal, symlink race, and time-of-check-time-of-use race condition issues.

The two vulnerabilities — CVE-2022-29799 and CVE-2022-29800 — have been fixed by the maintainer of the open-source project and Microsoft is recommending that Linux admins opt for strong monitoring of the platform’s operating system and its components.  

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