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Fencer Intel
high 7.5

CVE-2020-36221 in the critical feed json

An integer underflow was discovered in OpenLDAP before 2.4.57 leading to slapd crashes in the Certificate Exact Assertion processing, resul…

published 5y ago modified 26d ago also BIT-openldap-2020-36221 , EUVD-2020-23766 , JLSEC-2026-163

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
85.0%
EPSS 85.0% chance of exploitation in 30 days, percentile 99.7%
public exploits
0
none known

Summary

An integer underflow was discovered in OpenLDAP before 2.4.57 leading to slapd crashes in the Certificate Exact Assertion processing, resulting in denial of service (schema_init.c serialNumberAndIssuerCheck).

Patch / fix

  • bitnami openldap 2.4.57
  • julia OpenLDAPClient_jll 2.5.14+0
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • openldap Debian 14, Debian 13, Debian 12 2.4.57+dfsg-1

debian advisories DEBIAN-CVE-2020-36221

  • openldap Ubuntu 16.04 LTS 2.4.42+dfsg-2ubuntu3.12
  • openldap Ubuntu 18.04 LTS 2.4.45+dfsg-1ubuntu1.9
  • openldap Ubuntu 20.04 LTS 2.4.49+dfsg-2ubuntu1.6
  • openldap Ubuntu Pro 14.04 LTS 2.4.31-1+nmu2ubuntu8.5+esm7

ubuntu advisories UBUNTU-CVE-2020-36221

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openldap2 SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 2.4.26-0.74.26.1
  • openldap2-client SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 2.4.26-0.74.26.1
  • openldap2-client-openssl1 SLES 11-SECURITY 2.4.26-0.74.26.1
  • openldap2 SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +13 more 2.4.46-9.48.1
  • openldap2 SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +14 more 2.4.41-18.83.1
  • openldap2 SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +2 more 2.4.41-39.1

suse advisories SUSE-SU-2021:14700-1SUSE-SU-2021:0723-1SUSE-SU-2021:0693-1SUSE-SU-2021:0692-1

  • openldap2 openSUSE Leap 15.2 2.4.46-lp152.14.18.1

opensuse advisories openSUSE-SU-2021:0408-1

  • openldap Alpine 3.24, Alpine 3.23, Alpine 3.22 +9 more 2.4.57-r0

alpine advisories ALPINE-CVE-2020-36221

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openldap Arch Linux 2.4.57-1

arch linux advisories AVG-1489

Is CVE-2020-36221 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-36221 updated cvss 7.5

openldap: Integer underflow in serialNumberAndIssuerCheck in schema_init.c

  • Red Hat Enterprise Linux 6 openldap, compat-openldap, openldap-clients, openldap-servers, openldap-servers-sql Red Hat Enterprise Linux 7 openldap, compat-openldap, openldap-clients, openldap-servers, openldap-servers-sql
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 openldap, openldap-clients, openldap-servers Red Hat Enterprise Linux 9 openldap, openldap-compat, openldap-clients
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-348-10 updated cvss 7.5

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

84.99% chance of exploitation in the next 30 days, higher than 99.7% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami openldap
<2.4.57
2.4.57
julia OpenLDAPClient_jll
<2.5.14+0
2.5.14+0

Affected products

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness
  • CWE-191 Integer Underflow (Wrap or Wraparound)

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.