CVE-2026-103552 in Context: Six LDAP API Issues in One Apache Release

Overview

Apache's 2 October 2026 advisory batch covered eight CVEs across three projects. Six of them fell on the Apache Directory LDAP API, and CVE-2026-103552 is one of that group: a stack-based buffer overflow, CWE-121, rated 7.3 under CVSS v3, corrected in version 1.2.9. Seeing it alone hides the shape of the maintenance window.

The cluster

The LDAP API problems cover different weak points in the same code base. CVE-2026-103877 is a deserialization issue in which a rogue server or a pre-TLS attacker can answer a schema request with a serialized Java class, which Apache describes as allowing some potential remote code execution. CVE-2026-103552 is the stack overflow driven by deeply nested search filters. CVE-2026-102731 pushes the client into an oversized memory allocation. Two further issues let a crafted telephone number or a high-cost bcrypt hash pin a CPU core, and CVE-2026-103878 can expose plaintext during a StartTLS upgrade.

Why the grouping matters

Four of the six land in the 2.1.0 line before 2.1.9 and two, including this one, in the 1.2.0 line before 1.2.9. An operator who reads only the CVE that made the headlines may upgrade one branch and leave the other exposed. The cluster also shows a common theme: a library that accepts untrusted input needs defensive bounds on recursion, allocation size, and work performed per request.

Impact and exploitation

Apache reported no confirmed exploitation and no public proof of concept for the batch. The confirmed risk is denial of service and integrity loss in directory-facing processes, with potential code execution unproven for the overflow record.

Affected scope

Apache Directory LDAP API 2.1.0 before 2.1.9 (four CVEs) and 1.2.0 before 1.2.9 (two CVEs, including CVE-2026-103552).

Exposure context

ZoomEye reports 154 hosts matching the ApacheDS fingerprint; a CVE-scoped query returned no indexed assets. The fingerprint describes reachable product instances, not confirmed vulnerable versions.

Remediation

Upgrade both affected lines to 2.1.9 and 1.2.9 respectively, rebuild dependent applications, and verify the classpath. Where a directory listener is internet-facing without a pressing need, close it while the upgrade completes.

References

• SecurityOnline advisory roundup: https://securityonline.info/apache-openoffice-vulnerability-ldap-api-traffic-server/
• NVD record for CVE-2026-103552: https://nvd.nist.gov/vuln/detail/CVE-2026-103552