Is CVE-2023-51764 in the CISA KEV catalog?

No. CVE-2023-51764 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2023-51764?

CVE-2023-51764 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2023-51764?

CVE-2023-51764 has an EPSS score of 2.60% (83th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2023-51764?

Upgrade postfix on debian 11 to 3.5.23-0+deb11u1 or later. Fixes are available for 38 affected products.

CVE & CISA-KEV Catalog

CVE-2023-51764

MEDIUMEPSS 83th pctl

5.3

CVSS v3

NVD

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.

CWE-345

How to fix

Remediation Available

postfixDebian

Fixed in:3.5.23-0+deb11u1CVE-2023-51764

Fixed in:3.7.9-0+deb12u1CVE-2023-51764

Fixed in:3.8.4-1CVE-2023-51764

postfixRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfixRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-cdbRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-cdbRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-cdb-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-cdb-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-debugsourceRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-debugsourceRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-ldapRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-ldapRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-ldap-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-ldap-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-lmdbRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-lmdbRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-lmdb-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-lmdb-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-mysqlRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-mysqlRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-mysql-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-mysql-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pcreRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pcreRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pcre-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pcre-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-perl-scriptsRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-perl-scriptsRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pgsqlRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pgsqlRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pgsql-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-pgsql-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-sqliteRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-sqliteRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-sqlite-debuginfoRed Hat / RHEL

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfix-sqlite-debuginfoRocky

Fixed in:2:3.5.25-1.el9RHSA-2024:9243

postfixUbuntu

Fixed in:2.11.0-1ubuntu1.2+esm3USN-6591-2

Fixed in:2.11.0-1ubuntu1.2+esm2USN-6591-1

Fixed in:3.1.0-3ubuntu0.4+esm2USN-6591-1

Fixed in:3.1.0-3ubuntu0.4+esm3USN-6591-2

Fixed in:3.3.0-1ubuntu0.4+esm3USN-6591-2

Fixed in:3.3.0-1ubuntu0.4+esm2USN-6591-1

Fixed in:3.4.13-0ubuntu1.3USN-6591-1

Fixed in:3.4.13-0ubuntu1.4USN-6591-2

Fixed in:3.6.4-1ubuntu1.3USN-6591-2

Fixed in:3.6.4-1ubuntu1.2USN-6591-1

Fixed in:3.8.1-2ubuntu0.1USN-6591-1

Fixed in:3.8.1-2ubuntu0.2USN-6591-2

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Exploit Intelligence

2.60%probability of exploitation in 30 days

83rdpercentile

Elevated risk: more likely to be exploited than 83% of all known CVEs.

References

Exploit4

Third-Party Advisory5

Technical Description1

fahrplan.events.ccc.de

Other references9

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-04.