CVE-2020-27840

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 3.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-05-12 · updated 2026-06-17
Weakness: CWE-125

Description

A flaw was found in samba. Spaces used in a string around a domain name (DN), while supposed to be ignored, can cause invalid DN strings with spaces to instead write a zero-byte into out-of-bounds memory, resulting in a crash. The highest threat from this vulnerability is to system availability.

Affected products

Debian Linux: 9.0, 10.0
Fedoraproject Fedora: 32, 33, 34
Samba: from 4.0.0 before 4.12.13; from 4.13.0 before 4.13.6; from 4.14.0 before 4.14.1 — fixed in 4.12.13, 4.13.6, 4.14.1

How to fix

Upgrade to a fixed version: Samba 4.12.13, 4.13.6, 4.14.1. Check the vendor advisory for mitigations.

References

https://bugzilla.redhat.com/show_bug.cgi?id=1941400
https://lists.debian.org/debian-lts-announce/2021/03/msg00036.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VLZ74IF2N75VQSIHBL4B3P5WKWQCXSRY/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/X5J3B6PN5XMXF3OHYBNHDKZ3XFSUGY4L/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZXP3ONIY6MB4C5LDZV4YL5KJCES3UX24/
https://security.gentoo.org/glsa/202105-22
https://security.netapp.com/advisory/ntap-20210326-0007/
https://www.debian.org/security/2021/dsa-4884
https://www.samba.org/samba/security/CVE-2020-27840.html
https://bugzilla.redhat.com/show_bug.cgi?id=1941400
https://lists.debian.org/debian-lts-announce/2021/03/msg00036.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VLZ74IF2N75VQSIHBL4B3P5WKWQCXSRY/

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