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CVE-2023-51764

5.3 · MEDIUM

Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in…

Published Dec 24, 2023CWE-345EPSS 2.63%

Overview

CVE-2023-51764 is a medium-severity vulnerability. It was published on December 24, 2023 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in recent versions). Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Postfix supports <LF>.<CR><LF> but some other popular e-mail servers do not. To prevent attack variants (by always disallowing <LF> without <CR>), a different solution is required, such as the smtpd_forbid_bare_newline=yes option with a Postfix minimum version of 3.5.23, 3.6.13, 3.7.9, 3.8.4, or 3.9.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refwww.openwall.com/lists/oss-security/2023/12/24/1Refwww.openwall.com/lists/oss-security/2023/12/25/1Refwww.openwall.com/lists/oss-security/2024/05/09/3Refaccess.redhat.com/security/cve/CVE-2023-51764Refbugzilla.redhat.com/show_bug.cgi?id=2255563Reffahrplan.events.ccc.de/congress/2023/fahrplan/events/11782.htmlGitHubgithub.com/duy-31/CVE-2023-51764GitHubgithub.com/eeenvik1/CVE-2023-51764Reflists.debian.org/debian-lts-announce/2024/01/msg00020.htmlReflists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JQ5WXFCW2N6G2PH3JXDTYW5PH5EBQEGO/

How CyberStrike helps

Frequently asked questions

What is CVE-2023-51764?

CVE-2023-51764 is a medium-severity vulnerability. It was published on December 24, 2023 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2023-51764?

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2023-51764?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2023-51764?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2023-51764 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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