RHSA-2026:51034HighCVSS 7.5

Red Hat Security Advisory: postfix security update

Published
August 6, 2026
Last Modified
August 6, 2026

🔗 CVE IDs covered (1)

CVE-2026-43964 →

📋 Description

CVE-2026-43964 — postfix: buffer over-read via malformed enhanced status code

🎯 Affected products58

  • Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4)
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
  • postfix-2:3.5.8-1.el8_4.1.src as a component of Red Hat Enterprise Linux BaseOS AUS (v.8.4)
  • postfix-2:3.5.8-1.el8_4.1.src as a component of Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
  • postfix-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS AUS (v.8.4)
  • postfix-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
  • postfix-cdb-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • postfix-cdb-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • postfix-cdb-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • postfix-cdb-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • postfix-cdb-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS AUS (v.8.4)
  • postfix-cdb-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
  • postfix-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • postfix-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • postfix-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS AUS (v.8.4)
  • postfix-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
  • postfix-debugsource-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • postfix-debugsource-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • postfix-debugsource-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS AUS (v.8.4)
  • postfix-debugsource-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
  • postfix-ldap-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • postfix-ldap-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • postfix-ldap-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • postfix-ldap-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • postfix-ldap-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS AUS (v.8.4)
  • postfix-ldap-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
  • postfix-lmdb-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.4)
  • postfix-lmdb-debuginfo-2:3.5.8-1.el8_4.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
  • +28 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Workaround: To mitigate this vulnerability, review and adjust the following Postfix configurations: - DNSBL: Remove the $rbl_text variable from the rbl_reply_maps and default_rbl_reply settings to prevent triggers via malicious DNSBL TXT responses. - Policy Servers and Milters: Ensure any connected policy daemons or milters return fully RFC-compliant enhanced status codes. They must not return codes that lack text after the third digit (e.g., they should return 5.7.1 Rejected rather than just 5.7.1). - Access Tables and Content Checks: Audit custom access tables, header_checks, body_checks, and transport_maps (specifically error transports) to confirm that any manually defined rejection messages or status codes include descriptive text following the numeric code.

🔗 References (4)