CVE-2021-3492 Ubuntu linux kernel shiftfs file system double free vulnerability

What is CVE-2021-3492?

CVE-2021-3492 is a high-severity use after free vulnerability in Canonical Ubuntu Linux, published on 17 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copy_from_user() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could use this to cause a denial of service (kernel memory exhaustion) or gain privileges via executing arbitrary code. AKA ZDI-CAN-13562.

Weakness: CWE-415, CWE-401

Which versions are affected by CVE-2021-3492?

It affects 1 product.

Products include Canonical Ubuntu Linux.

How do I fix CVE-2021-3492?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2021-3492 being exploited?

There is no known exploitation of CVE-2021-3492 in the wild and no public exploit code.

Public exploit code: 1 proofs of concept on GitHub.

Other vulnerabilities in Canonical Ubuntu Linux

• CVE-2020-11651 SaltStack Salt Authentication Bypass Exploited Critical 9.8
• CVE-2020-7247 OpenSMTPD Remote Code Execution Exploited Critical 9.8
• CVE-2019-16928 Exim Out-of-bounds Write Exploited Critical 9.8
• CVE-2018-6789 Exim Buffer Overflow Exploited Critical 9.8
• CVE-2015-2590 Oracle Java SE and Java SE Embedded Remote Code Execution Exploited Critical 9.8

All Canonical Ubuntu Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-hr5j-7qj8-mpp3, LSN-0077-1, UBUNTU-CVE-2021-3492.