#VU50395 Integer underflow in OpenLDAP - CVE-2020-36228

Vulnerability identifier: #VU50395

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-36228

CWE-ID: CWE-191

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
OpenLDAP
Server applications / Directory software, identity management

Vendor: OpenLDAP.org

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to integer underflow when processing the certificate list exact assertion. A remote attacker can send a specially crafted request to the slapd, trigger integer underflow and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

OpenLDAP: 2.4.3 - 2.4.56

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External links
https://bugs.openldap.org/show_bug.cgi?id=9427
https://git.openldap.org/openldap/openldap/-/commit/91dccd25c347733b365adc74cb07d074512ed5ad
https://git.openldap.org/openldap/openldap/-/tags/OPENLDAP_REL_ENG_2_4_57
https://lists.debian.org/debian-lts-announce/2021/02/msg00005.html
https://www.debian.org/security/2021/dsa-4845

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.