CVE-2020-36227Public exploitNetwork attack vector

Service hang via self-referential Cancel request

Published Jan 25, 2021 · Updated Aug 4, 2024

Infinite-loop denial of service in OpenLDAP slapd before 2.4.57 allows remote attackers to hang the directory server with a crafted Cancel request. The cancel_extop handler fails to detect when a Cancel operation targets its own message ID, then waits indefinitely for that operation to finish. No authentication is required; repeated requests consume all command-handling threads and 100% CPU until slapd stops answering new queries.

CVSS severity7.5
High
EPSS probability77.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Infinite-loop denial of service in OpenLDAP slapd before 2.4.57 allows remote attackers to hang the directory server with a crafted Cancel request. The cancel_extop handler fails to detect when a Cancel operation targets its own message ID, then waits indefinitely for that operation to finish. No authentication is required; repeated requests consume all command-handling threads and 100% CPU until slapd stops answering new queries.

The record

CVE
CVE-2020-36227
Published
Jan 25, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 25, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Application or System Exploitation

Public exploit references

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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