CVE-2021-4091Network attack vector

Service crash via shared virtual-attribute context

Published Feb 18, 2022 · Updated Nov 3, 2025

Double-free in 389 Directory Server 389-ds-base 1.3.10.2 allows remote attackers to crash the LDAP service via search requests. During a persistent search, slapi_pblock_clone leaves the worker's private pblock and the spawned thread's cloned pblock pointing to the same pb_vattr_context, so both cleanup paths free it. No authentication or user interaction is required; a series of network search requests can terminate ns-slapd and interrupt directory service.

CVSS severity7.5
High
EPSS probability2.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double-free in 389 Directory Server 389-ds-base 1.3.10.2 allows remote attackers to crash the LDAP service via search requests. During a persistent search, slapi_pblock_clone leaves the worker's private pblock and the spawned thread's cloned pblock pointing to the same pb_vattr_context, so both cleanup paths free it. No authentication or user interaction is required; a series of network search requests can terminate ns-slapd and interrupt directory service.

The record

CVE
CVE-2021-4091
Published
Feb 18, 2022
Updated
Nov 3, 2025
Vendor
389 Directory Server
Product
389 Directory Server
Classifications
CWE-415, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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=389-ds-base-1.3.10.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · 389 Directory Serverversion=389-ds-base-1.3.10.2

Published CVSS scores

7.5Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9SUSECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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