CVE-2026-43964 Denial of service in Postfix
Low 3.7
Published
Updated
Check this codebase for CVE-2026-43964 and fix it if it is affected.
What it is: CVE-2026-43964 is a low-severity denial of service vulnerability in Postfix, published on 4 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43964 in the wild and no public exploit code.
Affected product: Postfix. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2026-43964/ (Markdown: https://insights.sbomify.com/CVE-2026-43964/index.md)
A buffer over-read in Postfix allows attackers to crash the mail server by sending a malformed enhanced status code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43964?
CVE-2026-43964 is a low-severity denial of service vulnerability in Postfix, published on 4 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Postfix before 3.8.16, 3.9 before 3.9.10, and 3.10 before 3.10.9 sometimes allows a buffer over-read and process crash via an enhanced status code that lacks text after the third number.
Weakness: CWE-193
Which versions are affected by CVE-2026-43964?
It affects 1 product.
Linux distribution packages (40)
postfix AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-cdb AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-ldap AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-lmdb AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-mysql AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-pcre AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-perl-scripts AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-pgsql AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix-sqlite AlmaLinux:10 | All versions | 2:3.8.5-10.el10_2 |
postfix AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix-cdb AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix-ldap AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix-mysql AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix-pcre AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix-perl-scripts AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix-pgsql AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix-sqlite AlmaLinux:8 | All versions | 2:3.5.8-8.el8_10 |
postfix AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-cdb AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-ldap AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-lmdb AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-mysql AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-pcre AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-perl-scripts AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-pgsql AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix-sqlite AlmaLinux:9 | All versions | 2:3.5.25-3.el9_8 |
postfix Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-cdb Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-cdb-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-debugsource Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-ldap Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-ldap-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-lmdb Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-lmdb-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-mysql Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-mysql-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-pcre Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-pcre-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
postfix-perl-scripts Red Hat:enterprise_linux:10.2 | All versions | 2:3.8.5-10.el10_2 |
Products include Postfix Postfix.
How do I fix CVE-2026-43964?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-43964 being exploited?
There is no known exploitation of CVE-2026-43964 in the wild and no public exploit code.
Other vulnerabilities in Postfix
Sources
Also known as ALSA-2026:25930, ALSA-2026:25932, ALSA-2026:26205, AZL-85709, CLSA-2026-1778874422, CLSA-2026-1778938383 and 35 more.