CVE-2020-36221Network attack vector

Unauthenticated service crash via malformed certificate assertion

Published Jan 25, 2021 · Updated Aug 4, 2024

Integer underflow in OpenLDAP slapd before 2.4.57 allows remote attackers to crash the service via crafted Certificate Exact Assertion input. In schema_init.c, serialNumberAndIssuerCheck fails to reject malformed brace or quote termination, then advances pointers and subtracts lengths beyond the remaining input. No authentication or user interaction is required; successful exploitation interrupts directory service availability without reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability84.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer underflow in OpenLDAP slapd before 2.4.57 allows remote attackers to crash the service via crafted Certificate Exact Assertion input. In schema_init.c, serialNumberAndIssuerCheck fails to reject malformed brace or quote termination, then advances pointers and subtracts lengths beyond the remaining input. No authentication or user interaction is required; successful exploitation interrupts directory service availability without reported data disclosure or modification.

The record

CVE
CVE-2020-36221
Published
Jan 25, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-191, T1499
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 exploitUnconfirmed

Weakness, pattern, technique

CWE-191Integer Underflow (Wrap or Wraparound)
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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