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CVE-2020-16120— Unprivileged overlay + shiftfs read access

Quick assessment

Affected
Linux kernel Linux kernel
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel Overlayfs Unprivileged User中存在安全漏洞。该漏洞允许攻击者获取敏感信息。

CVSS 5.1 · Medium EPSS 0.41% · P33
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I. Basic Information for CVE-2020-16120

Vulnerability Information
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Vulnerability Title
Unprivileged overlay + shiftfs read access
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
特权授予不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel Overlayfs Unprivileged User中存在安全漏洞。该漏洞允许攻击者获取敏感信息。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux kernel Linux kernel 5.11-stable ~ 5.11.0 -

II. Public POCs for CVE-2020-16120

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III. Intelligence Information for CVE-2020-16120

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Vendor Advisories for CVE-2020-16120 (4)

Mailing List Discussions for CVE-2020-16120 (1)

Other References for CVE-2020-16120 (6)

IV. Related Vulnerabilities

Same product: Linux kernel
Same vendor: Linux kernel
Same weakness: CWE-266

V. Comments for CVE-2020-16120

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