CVE-2023-26438: Open-Xchange Appsuite Backend

Low severity, CVSS 3.1. EPSS: 0.6% chance of exploitation in the next 30 days.

External service lookups for a number of protocols were vulnerable to a time-of-check/time-of-use (TOCTOU) weakness, involving the JDK DNS cache. Attackers that were timing DNS cache expiry correctly were able to inject configuration that would bypass existing network deny-lists. Attackers could exploit this weakness to discover the existence of restricted network infrastructure and service availability. Improvements were made to include deny-lists not only during the check of the provided connection data, but also during use. No publicly available exploits are known.

Affected products

• Open-Xchange Open-Xchange Appsuite Backend: version 7.10.6 only; version 8.10.0 only

Published 2023-08-02. Last modified 2026-06-17.