#VU52748 Out-of-bounds read in Samba - CVE-2021-20254

Vulnerability identifier: #VU52748

Vulnerability risk: Medium

CVSSv4.0: 0.5 [CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-20254

CWE-ID: CWE-125

Exploitation vector: Local network

Exploit availability: No

Vulnerable software:
Samba
Server applications / Directory software, identity management

Vendor: Samba

Description

The vulnerability allows a remote user to gain access to potentially sensitive information.

The vulnerability exists due to a boundary condition when mapping Windows group identities (SIDs) into unix group identities (gids), which resulted into negative idmap cache entries created in the Samba server process token. An attacker who can manage to trigger the vulnerability can crash the Samba server or potentially perform unauthorized actions on the system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Samba: 3.6.0 - 3.6.25, 4.0.0 - 4.0.26, 4.1.0 - 4.14.3, 4.2.0 - 4.2.14, 4.3.0 - 4.3.13, 4.4.0 rc4 - 4.4.16, 4.5.0 - 4.5.16, 4.6.0 - 4.6.16, 4.7.0 - 4.7.12, 4.8.0 - 4.8.12, 4.9.0 - 4.9.18

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External links
https://www.samba.org/samba/security/CVE-2021-20254.html

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

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