CVE-2021-3670Network attack vector

Authenticated service interruption via uncapped LDAP searches

Published Aug 23, 2022 · Updated Feb 13, 2025

Resource exhaustion in Samba AD DC LDAP 4.1 and later allows remote authenticated users to interrupt directory service via complex searches. ldapsrv_SearchRequest passed the client-requested time limit to ldb_set_timeout without capping it at the server's MaxQueryDuration policy, and filter evaluation lacked interruption points. A domain credential and network access to LDAP are required; enough concurrent long-running searches can occupy all LDAP threads.

CVSS severity6.5
Medium
EPSS probability2.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Samba AD DC LDAP 4.1 and later allows remote authenticated users to interrupt directory service via complex searches. ldapsrv_SearchRequest passed the client-requested time limit to ldb_set_timeout without capping it at the server's MaxQueryDuration policy, and filter evaluation lacked interruption points. A domain credential and network access to LDAP are required; enough concurrent long-running searches can occupy all LDAP threads.

The record

CVE
CVE-2021-3670
Published
Aug 23, 2022
Updated
Feb 13, 2025
Vendor
PPP Project
Product
Samba
Classifications
CWE-770, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 23, 2022CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Affects Samba 4.1 and newer.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

PPP Project · Sambaversion=Affects Samba 4.1 and newer.

Published CVSS scores

6.5Red HatCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.5SUSECVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.004Application or System Exploitation DoS

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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