A remote denial-of-service vulnerability (CVE-2026-43964) exists in Postfix due to incorrect handling of certain enhanced status codes, allowing an attacker to crash the service via specially crafted network traffic. The vulnerability affects multiple Ubuntu LTS releases, including Postfix versions 3.10.6-4ubuntu2.1 on Ubuntu 26.04, 3.10.2-1ubuntu2.1 on Ubuntu 25.10, 3.8.6-1ubuntu0.1 on Ubuntu 24.04, and 3.6.4-1ubuntu1.4 on Ubuntu 22.04. A standard system update will apply the necessary patches to correct the issue.
Ubuntu Security Notices USN-8253-1 USN-8253-1: Postfix vulnerability Publication date 7 May 2026 Overview Postfix could be made to crash if it received specially crafted network traffic. Releases 26.04 LTS 25.10 24.04 LTS 22.04 LTS Open side navigation Close side navigation Packages Details Update instructions References Packages postfix - High-performance mail transport agent Details Kamil Frankowicz discovered that Postfix incorrectly handled certain enhanced status codes. A remote attacker could possibly use this issue to cause Postfix to crash, resulting in a denial of service. Kamil Frankowicz discovered that Postfix incorrectly handled certain enhanced status codes. A remote attacker could possibly use this issue to cause Postfix to crash, resulting in a denial of service. Update instructions In general, a standard system update will make all the necessary changes. Learn more about how to get the fixes. The problem can be corrected by updating your system to the following package versions: Ubuntu Release Package Version 26.04 LTS resolute postfix – 3.10.6-4ubuntu2.1 25.10 questing postfix – 3.10.2-1ubuntu2.1 24.04 LTS noble postfix – 3.8.6-1ubuntu0.1 22.04 LTS jammy postfix – 3.6.4-1ubuntu1.4 Reduce your security exposure Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines. Get Ubuntu Pro References CVE-2026-43964 CVE-2026-43964