CVE-2021-20254

Name: CVE-2021-20254
Creator: NVD / NIST
Published: 2021-05-05T14:15:07.883+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.8/10EPSS 1.62%

Last modified Jun 17, 2026

CVE-2021-20254 is a medium-severity vulnerability rated 6.8/10 on the CVSS scale. A flaw was found in samba. The Samba smbd file server must map Windows group identities (SIDs) into unix group ids (gids). EPSS estimates a 1.62% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.8/10

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

EPSS Probability

1.62%

73.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-125

Affected Software

Vendor	Product	Versions
Samba	Samba	>= 3.6.0, < 4.12.15
Samba	Samba	>= 4.13.0, < 4.13.8
Samba	Samba	>= 4.14.0, < 4.14.4
Fedoraproject	Fedora	32
Fedoraproject	Fedora	33
Redhat	Enterprise Linux	7.0
Redhat	Enterprise Linux	8.0
Debian	Debian Linux	9.0

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

Timeline

Published: May 5, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20254?

How severe is CVE-2021-20254?

CVE-2021-20254 has a CVSS score of 6.8/10 (MEDIUM severity). The EPSS model estimates a 1.62% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20254?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20254?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST