Fedora Postfix Buffer Over-Read Vulnerability Advisory
Severity: Medium (Score: 57.9)
Sources: Linuxsecurity
Published: · Updated:
Keywords: jaroslav, version, resolves, cve-2026-43964, fedora, postfix, buffer
Severity indicators: critical, CVE:CVE-2026-43964
Summary
On May 18, 2026, an update was released for Fedora versions addressing a critical buffer over-read vulnerability identified as CVE-2026-43964. This vulnerability allows for a buffer over-read via a malformed enhanced status code, potentially exposing sensitive information. The affected systems include all Fedora distributions using Postfix version 2:3.10.10-1. Users are advised to upgrade their systems using the 'dnf' update program to mitigate the risk. The CVE was published on May 4, 2026, and is categorized as a significant security concern. Administrators should prioritize applying the patch to prevent potential exploitation. Key Points: • CVE-2026-43964 is a critical buffer over-read vulnerability in Postfix. • Affected systems include all Fedora versions using Postfix 2:3.10.10-1. • Users are urged to apply the patch immediately using the 'dnf' update program.
Detailed Analysis
**Impact** The vulnerability affects all Fedora 43 and Fedora 44 users running Postfix mail servers. The buffer over-read flaw could lead to potential service disruptions or data leakage when processing malformed enhanced status codes. No specific sectors, geographies, or data volumes at risk are detailed in the available information. **Technical Details** The issue is a buffer over-read vulnerability identified as CVE-2026-43964, triggered via malformed enhanced status codes in Postfix. The flaw was reported under Bug #2477885 and affects Postfix version 3.10.10-1. The attack vector involves sending crafted mail status codes to exploit memory handling during mail processing. No malware, tools, or infrastructure details are provided. **Recommended Response** Apply the updated Postfix package version 3.10.10-1 immediately using the Fedora dnf update advisories FEDORA-2026-e9fc21d7e2 (Fedora 43) or FEDORA-2026-5cf8cc5f32 (Fedora 44). Use the command `su -c 'dnf upgrade --advisory <advisory_id>'` to patch affected systems. Monitor mail server logs for unusual or malformed status codes and ensure mail server configurations follow best security practices. No additional IOCs or detection rules are specified.
Source articles (2)
- Fedora 44 Postfix Important Buffer Over-Read CVE-2026 — Linuxsecurity · 2026-06-02
* Mon May 18 2026 Jaroslav Škarvada - 2:3.10.10-1 - New version Resolves: CVE-2026-43964 * Mon May 18 2026 Jaroslav Škarvada - 2:3.10.10-1 - New version Resolves: CVE-2026-43964 [ 1 ] Bug #2477885 - C… - Fedora 43 Postfix Critical Buffer Over-read Fix Advisory 2026 — Linuxsecurity · 2026-06-02
* Mon May 18 2026 Jaroslav Škarvada - 2:3.10.10-1 - New version Resolves: CVE-2026-43964 * Mon May 18 2026 Jaroslav Škarvada - 2:3.10.10-1 - New version Resolves: CVE-2026-43964 [ 1 ] Bug #2477885 - C…
Timeline
- 2026-05-04 — CVE-2026-43964 published: CVE-2026-43964 was officially published, detailing a buffer over-read vulnerability in Postfix.
- 2026-05-18 — Fedora update released: An update was released for Fedora to address CVE-2026-43964, resolving the buffer over-read issue.
- 2026-06-02 — Advisory published: Linuxsecurity published advisories for Fedora 43 and 44 regarding CVE-2026-43964, urging users to upgrade.
CVEs
Related entities
- Cwe-125 - Out-of-bounds Read (Cwe)
- Fedora (Company)
- Postfix (Platform)