Hacking

CVE-2021-44731 Linux privilege escalation bug affects Canonical’s Snap Package Manager

Qualys experts found a new Linux privilege escalation vulnerability, tracked as CVE-2021-44731, in Canonical’s Snap Package Manager.

Canonical’s Snap software packaging and deployment system are affected by multiple vulnerabilities, including a privilege escalation flaw tracked as CVE-2021-44731 (CVSS score 7.8).

Snap is a software packaging and deployment system developed by Canonical for operating systems that use the Linux kernel. The packages, called snaps, and the tool for using them, snapd, work across a range of Linux distributions

The flaws have been discovered by Qualys researchers, the CVE-2021-44731 is the most severe one and is a race condition in the snap-confine’s setup_private_mount() function.

The snap-confine is a program used internally by snapd to construct the execution environment for snap applications. An unprivileged user can trigger the flaw to gain root privileges on the affected host.

“Successful exploitation of this vulnerability allows any unprivileged user to gain root privileges on the vulnerable host.” reads the post published by the experts. “As soon as the Qualys Research Team confirmed the vulnerability, we engaged in responsible vulnerability disclosure and coordinated with both vendor and open-source distributions in announcing this newly discovered vulnerability.”

Qualys experts also developed a PoC exploit for this issue that allows obtaining full root privileges on default Ubuntu installations.

Below is the full list of vulnerabilities discovered by the experts:

CVEDescription
CVE-2021-44731Race condition in snap-confine’s setup_private_mount()
CVE-2021-44730Hardlink attack in snap-confine’s sc_open_snapd_tool()
CVE-2021-3996Unauthorized unmount in util-linux’s libmount
CVE-2021-3995Unauthorized unmount in util-linux’s libmount
CVE-2021-3998Unexpected return value from glibc’s realpath()
CVE-2021-3999Off-by-one buffer overflow/underflow in glibc’s getcwd()
CVE-2021-3997Uncontrolled recursion in systemd’s systemd-tmpfiles

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Pierluigi Paganini

(SecurityAffairs – hacking, CVE-2021-44731)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.

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