CVE-2021-20254
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.
Does this matter?
Lower severity and a low EPSS score (1.62%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 3.1
- 6.8 MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 1.62% probability · 76th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-125
- Affected
- samba/samba · fedoraproject/fedora · redhat/enterprise linux · debian/debian linux
- Source
- secalert@redhat.com
EPSS 1.6% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1949442Issue Tracking, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/05/msg00023.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3EP2VJ73OVBPVSOSTVOMGIEQA3MWF6F7/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZAF6L2M6CNAJ2YYYGXPWETTW5YLCWTVT/
- https://security.gentoo.org/glsa/202105-22Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210430-0001/Third Party Advisory
- https://www.samba.org/samba/security/CVE-2021-20254.htmlVendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1949442Issue Tracking, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/05/msg00023.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3EP2VJ73OVBPVSOSTVOMGIEQA3MWF6F7/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZAF6L2M6CNAJ2YYYGXPWETTW5YLCWTVT/
- https://security.gentoo.org/glsa/202105-22Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210430-0001/Third Party Advisory
- https://www.samba.org/samba/security/CVE-2021-20254.htmlVendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.