# CVE-2026-12528: 389 Directory Server heap buffer overflow in ACI parsing

Source: https://junglewise.ai/threats/cve-2026-12528-389-directory-server-heap-buffer-overflow-in-aci-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-17. Updated: 2026-06-20  
License: CC BY 4.0 with a link back

CVE-2026-12528 · Severity: medium · CVSS 5.4 · Published 2026-06-17

389 Directory Server is an enterprise-grade LDAP server used to manage user identities and access controls. A flaw in how it processes Access Control Instructions (ACIs) allows an authenticated user to corrupt the server's memory by sending a specially crafted instruction. While this could lead to minor data corruption or instability, it typically requires the attacker to already have permissions to modify security settings.

## Quick answers

**Is CVE-2026-12528 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-12528 being exploited in the wild.

**How severe is CVE-2026-12528?** Medium severity, with a CVSS score of 5.4, published 17 June 2026.

**Which products and versions are affected?** 389ds 389 Directory Server 2.x; Red Hat Red Hat Directory Server 11, 12, 13; Red Hat Red Hat Enterprise Linux 7, 8, 9, 10.

**Is there a fix for CVE-2026-12528?** A patch was published on 2026-06-03: Upstream pull request submitted and merged. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-12528 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-12528?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-buffer overflow exists in the __aclp__normalize_acltxt() function within aclparse.c of 389 Directory Server. The vulnerability is caused by a failure to validate the length of an Access Control Instruction (ACI) string after whitespace stripping, leading to a 1-byte out-of-bounds write and subsequent out-of-bounds reads. An attacker with network access and LDAP 'write' privileges to the 'aci' attribute can trigger this flaw by submitting a malformed ACI string. While the 1-byte write is not easily weaponized for code execution in production builds, it can lead to silent heap corruption or service instability. A fix has been merged into the upstream main branch.

## Affected products

- 389ds 389 Directory Server 2.x
- Red Hat Red Hat Directory Server 11, 12, 13
- Red Hat Red Hat Enterprise Linux 7, 8, 9, 10

## Timeline

- 2026-06-03: patched: Upstream pull request submitted and merged.
- 2026-06-17: disclosed: Vulnerability disclosed and CVE assigned.
- 2026-06-17: advisory: Red Hat and NVD published advisory details.

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-12528](https://access.redhat.com/security/cve/CVE-2026-12528)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2489835](https://bugzilla.redhat.com/show_bug.cgi?id=2489835)
- [https://github.com/389ds/389-ds-base/pull/7542](https://github.com/389ds/389-ds-base/pull/7542)