CVE-2020-25710Network attack vector

Unauthenticated service crash via malformed CSN normalization

Published May 28, 2021 · Updated Aug 4, 2024

Reachable assertion in OpenLDAP Software before 2.4.56 allows remote attackers to crash slapd with a malicious LDAP packet. The csnNormalize23 routine normalizes malformed CSN input and asserts that its output pointer equals the input-buffer end instead of rejecting a length mismatch. No authentication or user interaction is required; reaching the assertion terminates the server process and interrupts LDAP service.

CVSS severity7.5
High
EPSS probability2.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in OpenLDAP Software before 2.4.56 allows remote attackers to crash slapd with a malicious LDAP packet. The csnNormalize23 routine normalizes malformed CSN input and asserts that its output pointer equals the input-buffer end instead of rejecting a length mismatch. No authentication or user interaction is required; reaching the assertion terminates the server process and interrupts LDAP service.

The record

CVE
CVE-2020-25710
Published
May 28, 2021
Updated
Aug 4, 2024
Vendor
OpenLDAP Foundation
Product
OpenLDAP Software
Classifications
CWE-617, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 28, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=openldap 2.4.56

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenLDAP Foundation · OpenLDAP Softwareversion=openldap 2.4.56

Published CVSS scores

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-617Reachable Assertion
T1499Endpoint Denial of Service

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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