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Vulnerability Details : CVE-2020-16120

Overlayfs did not properly perform permission checking when copying up files in an overlayfs and could be exploited from within a user namespace, if, for example, unprivileged user namespaces were allowed. It was possible to have a file not readable by an unprivileged user to be copied to a mountpoint controlled by the user, like a removable device. This was introduced in kernel version 4.19 by commit d1d04ef ("ovl: stack file ops"). This was fixed in kernel version 5.8 by commits 56230d9 ("ovl: verify permissions in ovl_path_open()"), 48bd024 ("ovl: switch to mounter creds in readdir") and 05acefb ("ovl: check permission to open real file"). Additionally, commits 130fdbc ("ovl: pass correct flags for opening real directory") and 292f902 ("ovl: call secutiry hook in ovl_real_ioctl()") in kernel 5.8 might also be desired or necessary. These additional commits introduced a regression in overlay mounts within user namespaces which prevented access to files with ownership outside of the user namespace. This regression was mitigated by subsequent commit b6650da ("ovl: do not fail because of O_NOATIMEi") in kernel 5.11.
Publish Date : 2021-02-10 Last Update Date : 2021-02-18
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- CVSS Scores & Vulnerability Types

CVSS Score
2.1
Confidentiality Impact Partial (There is considerable informational disclosure.)
Integrity Impact None (There is no impact to the integrity of the system)
Availability Impact None (There is no impact to the availability of the system.)
Access Complexity Low (Specialized access conditions or extenuating circumstances do not exist. Very little knowledge or skill is required to exploit. )
Authentication Not required (Authentication is not required to exploit the vulnerability.)
Gained Access None
Vulnerability Type(s)
CWE ID 269

- Products Affected By CVE-2020-16120

# Product Type Vendor Product Version Update Edition Language
1 OS Canonical Ubuntu Linux 14.04 * * * Version Details Vulnerabilities
2 OS Canonical Ubuntu Linux 16.04 * * * Version Details Vulnerabilities
3 OS Canonical Ubuntu Linux 18.04 * * * Version Details Vulnerabilities
4 OS Canonical Ubuntu Linux 20.04 * * * Version Details Vulnerabilities
5 OS Linux Linux Kernel * * * * Version Details Vulnerabilities

- Number Of Affected Versions By Product

Vendor Product Vulnerable Versions
Canonical Ubuntu Linux 4
Linux Linux Kernel 1

- References For CVE-2020-16120

https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84 CONFIRM
https://launchpad.net/bugs/1894980 UBUNTU
https://ubuntu.com/USN-4578-1 UBUNTU
https://www.openwall.com/lists/oss-security/2020/10/14/2 CONFIRM
https://launchpad.net/bugs/1900141 UBUNTU
https://ubuntu.com/USN-4576-1 UBUNTU
https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d CONFIRM
https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52 CONFIRM
https://ubuntu.com/USN-4577-1 UBUNTU
https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f CONFIRM
https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8 CONFIRM

- Metasploit Modules Related To CVE-2020-16120

There are not any metasploit modules related to this CVE entry (Please visit www.metasploit.com for more information)


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