CVE-2021-3670 Denial of service in samba

Medium 6.5 Published 23 Aug 2022 Updated 13 Feb 2025

Attackers can cause denial of service in Samba AD DC by bypassing MaxQueryDuration limits in LDAP operations.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2021-3670?

CVE-2021-3670 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 23 Aug 2022. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

MaxQueryDuration not honoured in Samba AD DC LDAP

Weakness: CWE-400

Which versions are affected by CVE-2021-3670?

It affects 3 products.

Linux distribution packages (11)

`ldb` SUSE:Enterprise Storage 7.1	All versions	`2.4.2-150300.3.15.1`
`samba` SUSE:Linux Enterprise High Availability Extension 15 SP4	All versions	`4.15.7+git.376.dd43aca9ab2-150400.3.5.3`
`ldb` SUSE:Linux Enterprise Micro 5.1	All versions	`2.4.2-150300.3.15.1`
`ldb` SUSE:Linux Enterprise Micro 5.2	All versions	`2.4.2-150300.3.15.1`
`ldb` SUSE:Linux Enterprise Module for Basesystem 15 SP3	All versions	`2.4.2-150300.3.15.1`
`ldb` SUSE:Linux Enterprise Module for Basesystem 15 SP4	All versions	`2.4.2-150400.4.3.11`
`samba` SUSE:Linux Enterprise Module for Basesystem 15 SP4	All versions	`4.15.7+git.376.dd43aca9ab2-150400.3.5.3`
`ldb` openSUSE:Leap 15.3	All versions	`2.4.2-150300.3.15.1`
`ldb` openSUSE:Leap 15.4	All versions	`2.4.2-150400.4.3.11`
`samba` openSUSE:Leap 15.4	All versions	`4.15.7+git.376.dd43aca9ab2-150400.3.5.3`
`ldb` openSUSE:Tumbleweed	All versions	`2.4.2-1.1`

Products include Fedoraproject Fedora, Redhat Storage, Samba Samba.

How do I fix CVE-2021-3670?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-3670 being exploited?

There is no known exploitation of CVE-2021-3670 in the wild and no public exploit code.

All Fedoraproject Fedora vulnerabilities

Sources

Also known as ALPINE-CVE-2021-3670, AZL-10662, DEBIAN-CVE-2021-3670, ECHO-5114-69fd-f87a, GHSA-p9j9-qqwf-j574, OESA-2022-1735 and 5 more.