CVE-2026-102731: Apache Directory LDAP API: Denial of service via excessive memory allocation in BER decode

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-02 · updated 2026-10-05
Weakness: CWE-789

Description

Memory allocation with excessive size value vulnerability in Apache Directory LDAP API. A malicious peer (or a MITM) can send a small BER-encoded response causing a large memory allocation before any data is received. This can lead to an OutOfMemoryError and denial of service. The client JVM OOMs (OutOfMemoryError bypasses the DecoderException handlers) or pins the large allocation per connection while the attacker stalls. A handful of connections exhausts any heap. The same bytes from an unauthenticated pre-bind client hit any embedding server that did not set MAX_PDU_SIZE_ATTR. This issue affects Apache Directory LDAP API: from 1.2.0 before 1.2.9. Users are recommended to upgrade to version 1.2.9, which fixes the issue.

Affected products

Apache Software Foundation Apache Directory LDAP API: from 1.2.0 before 1.2.9 — fixed in 1.2.9

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache Directory LDAP API 1.2.9. Check the vendor advisory for mitigations.

References

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