Vulnerability Report

CVE-2020-16120

Title: Linux Linux Kernel

Other

Proof Of Concept

No public PoC currently indexed for CVE-2020-16120.

CWE Category CWE-266
Published Date Feb 10, 2021
Modified Date Nov 21, 2024
Exploit Status Not Found
Score 5.1 CVSS v3.1
Exploit Probability (EPSS)
0.40%

Vulnerability Summary

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.

Impacted Vendors

L
linux 1
U
ubuntu 2
C
canonical 1

Reference Links

https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8 https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84 https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52 https://launchpad.net/bugs/1894980 https://launchpad.net/bugs/1900141 https://ubuntu.com/USN-4576-1 https://ubuntu.com/USN-4577-1 https://ubuntu.com/USN-4578-1 https://www.openwall.com/lists/oss-security/2020/10/14/2 https://git.kernel.org/linus/05acefb4872dae89e772729efb194af754c877e8 https://git.kernel.org/linus/48bd024b8a40d73ad6b086de2615738da0c7004f https://git.kernel.org/linus/56230d956739b9cb1cbde439d76227d77979a04d https://git.kernel.org/linus/b6650dab404c701d7fe08a108b746542a934da84 https://git.kernel.org/linus/d1d04ef8572bc8c22265057bd3d5a79f223f8f52 https://launchpad.net/bugs/1894980 https://launchpad.net/bugs/1900141 https://ubuntu.com/USN-4576-1 https://ubuntu.com/USN-4577-1 https://ubuntu.com/USN-4578-1 https://www.openwall.com/lists/oss-security/2020/10/14/2
CVSS v3.1
Source Entity [email protected]
Severity MEDIUM
5.1
Attack Vector
LOCAL
Complexity
HIGH
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS v3.1
Source Entity [email protected]
Severity MEDIUM
4.4
Attack Vector
LOCAL
Complexity
LOW
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
CVSS v2.0
Source Entity [email protected]
Severity LOW
2.1
Access Vector
N/A
Authentication
N/A
RAW VECTOR AV:L/AC:L/Au:N/C:P/I:N/A:N

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2020-16120 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

MODIFIED

Vulnerability data or affected products updated.

PUBLISHED

Vulnerability first announced in NVD.

Attack Vector Matrix

Access Vector LOCAL
Complexity HIGH
Privileges N/A
Interaction NONE
CVSS Vector String CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected Stack

No specific products linked.