Incorrect permission assignment in NFS server in Linux kernel

1) Incorrect permission assignment for critical resource

EUVDB-ID: #VU51240

Risk: Low

CVSSv3.1: 6.2 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-24394

CWE-ID: CWE-732 - Incorrect Permission Assignment for Critical Resource

Exploit availability: No

Description

The vulnerability allows a local user to bypass implemented security restrictions.

The vulnerability exists due to incorrect assignment of permissions on new filesystem objects when the filesystem lacks ACL support in fs/nfsd/vfs.c (in the NFS server). A local user can read and write arbitrary files on the system.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Linux kernel: 5.7 - 5.7.7

External links

http://lists.opensuse.org/opensuse-security-announce/2020-09/msg00007.html
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=962254
http://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.7.8
http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=22cf8419f1319ff87ec759d0ebdff4cbafaee832
http://security.netapp.com/advisory/ntap-20200904-0003/
http://usn.ubuntu.com/4465-1/
http://usn.ubuntu.com/4483-1/
http://usn.ubuntu.com/4485-1/

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.