CVE-2026-43964

CVE-2026-43964 is a low-severity vulnerability in Postfix with a CVSS 3.x base score of 3.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-193.

Key facts

• Severity: Low (CVSS 3.x base score 3.7)
• EPSS exploit prediction: 0% (33rd percentile)
• Actively exploited: Not listed in CISA KEV
• EU (EUVD) id: EUVD-2026-27115
• Weakness: CWE-193
• Affected product: Postfix
• Published: 2026-05-04
• Last modified: 2026-06-30

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.

Frequently asked questions

What is CVE-2026-43964?

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.

How severe is CVE-2026-43964?

CVE-2026-43964 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-43964 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-43964?

CVE-2026-43964 affects Postfix. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-43964?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-43964 have an EU (EUVD) identifier?

Yes. CVE-2026-43964 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-27115.

When was CVE-2026-43964 published?

CVE-2026-43964 was published on 2026-05-04 and last updated on 2026-06-30.

References

• https://www.mail-archive.com/[email protected]/msg00110.html
• http://www.openwall.com/lists/oss-security/2026/05/04/30
• https://access.redhat.com/errata/RHSA-2026:25930
• https://access.redhat.com/errata/RHSA-2026:25932
• https://access.redhat.com/errata/RHSA-2026:26205
• https://access.redhat.com/security/cve/CVE-2026-43964
• https://bugzilla.redhat.com/show_bug.cgi?id=2466488
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43964.json

Affected products (1)

• cpe:2.3:a:postfix:postfix:*:*:*:*:*:*:*:*

More vulnerabilities in Postfix

• CVE-2017-10140 — High (CVSS 7.8): Postfix before 2.11.10, 3.0.x before 3.0.10, 3.1.x before 3.1.6, and 3.2.x before 3.2.2 might allow local users to gain…
• CVE-2009-2939 — Medium (CVSS 6.9): The postfix.postinst script in the Debian GNU/Linux and Ubuntu postfix 2.5.5 package grants the postfix user write…
• CVE-2008-4977 — Medium (CVSS 6.9): postfix_groups.pl in Postfix 2.5.2 allows local users to overwrite arbitrary files via a symlink attack on the (1)…
• CVE-2011-1720 — Medium (CVSS 6.8): The SMTP server in Postfix before 2.5.13, 2.6.x before 2.6.10, 2.7.x before 2.7.4, and 2.8.x before 2.8.3, when certain…
• CVE-2011-0411 — Medium (CVSS 6.8): The STARTTLS implementation in Postfix 2.4.x before 2.4.16, 2.5.x before 2.5.12, 2.6.x before 2.6.9, and 2.7.x before…
• CVE-2012-0811 — Medium (CVSS 6.5): Multiple SQL injection vulnerabilities in Postfix Admin (aka postfixadmin) before 2.3.5 allow remote authenticated…

All CVEs affecting Postfix →

Other CWE-193 (Off-by-one Error) vulnerabilities

• CVE-2024-10442 — Critical (CVSS 10.0): Off-by-one error vulnerability in the transmission component in Synology Replication Service before 1.0.12-0066,…
• CVE-2026-53309 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: ocfs2/dlm: fix off-by-one in dlm_match_regions()…
• CVE-2024-38441 — Critical (CVSS 9.8): Netatalk before 3.2.1 has an off-by-one error and resultant heap-based buffer overflow because of setting ibuf[len] to…
• CVE-2023-46853 — Critical (CVSS 9.8): In Memcached before 1.6.22, an off-by-one error exists when processing proxy requests in proxy mode, if \n is used…
• CVE-2023-38429 — Critical (CVSS 9.8): An issue was discovered in the Linux kernel before 6.3.4. fs/ksmbd/connection.c in ksmbd has an off-by-one error in…
• CVE-2022-34970 — Critical (CVSS 9.8): Crow before 1.0+4 has a heap-based buffer overflow via the function qs_parse in query_string.h. On successful…

Browse all CWE-193 (Off-by-one Error) vulnerabilities →