CVE-2026-102731 Apache Directory LDAP API: Denial of service via excessive memory allocation in BER decode
A malicious peer can cause denial of service in applications using the Apache Directory LDAP API by triggering excessive memory allocation during BER decoding.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-102731?
CVE-2026-102731 is a high-severity denial of service vulnerability in Apache Directory LDAP API, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-789
Which versions are affected by CVE-2026-102731?
How do I fix CVE-2026-102731?
No fix has been published for CVE-2026-102731 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-102731 being exploited?
There is no known exploitation of CVE-2026-102731 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-102731, GHSA-h24g-pjpf-8f2m, UBUNTU-CVE-2026-102731.