Overview
- 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
- security@ubuntu.com
- NVD status
- Analyzed
Risk scores
CVSS 3.1
- Type
- Primary
- Base score
- 4.4
- Impact score
- 3.6
- Exploitability score
- 0.8
- Vector string
- CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
- Severity
- MEDIUM
CVSS 2.0
- Type
- Primary
- Base score
- 2.1
- Impact score
- 2.9
- Exploitability score
- 3.9
- Vector string
- AV:L/AC:L/Au:N/C:P/I:N/A:N
Weaknesses
- nvd@nist.gov
- NVD-CWE-Other
- security@ubuntu.com
- CWE-266
Social media
- Hype score
- Not currently trending
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