A flaw was found in samba. The Samba smbd file server must map Windows group identities (SIDs) into unix group ids (gids). The code that performs this had a flaw that could allow it to read data beyond the end of the array in the case where a negative cache entry had been added to the mapping cache. This could cause the calling code to return those values into the process token that stores the group membership for a user. The highest threat from this vulnerability is to data confidentiality and integrity.
https://security.netapp.com/advisory/ntap-20210430-0001/
https://www.samba.org/samba/security/CVE-2021-20254.html
https://bugzilla.redhat.com/show_bug.cgi?id=1949442
https://security.gentoo.org/glsa/202105-22
https://lists.debian.org/debian-lts-announce/2021/05/msg00023.html
Source: MITRE
Published: 2021-05-05
Updated: 2021-06-24
Type: CWE-125
Base Score: 4.9
Vector: AV:N/AC:M/Au:S/C:P/I:P/A:N
Impact Score: 4.9
Exploitability Score: 6.8
Severity: MEDIUM
Base Score: 6.8
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Impact Score: 5.2
Exploitability Score: 1.6
Severity: MEDIUM