CVE-2026-76560
Description
A flaw was found in 389 Directory Server. The SELFDN ACI bind-rule evaluator incorrectly matches an anonymous LDAP client's empty bind DN against an empty stored attribute value, allowing an unauthenticated client to satisfy access control checks intended to require a matching authenticated identity. This can allow an anonymous LDAP client to perform an operation, such as adding or modifying a directory entry, that a SELFDN-based ACI intended to restrict to a specific authenticated user.
Statement
This flaw affects any 389 Directory Server (or Red Hat Directory Server) deployment that defines an ACI using a userattr="attribute#SELFDN" or userattr="attribute#USERDN" bind rule on an attribute that is permitted to hold an explicit empty value. Red Hat Directory Server does not ship such an ACI by default; real-world impact depends on whether a specific deployment or consuming application defines an ACI of this shape.
Mitigation
Until a fix is available, review all ACIs using userattr="...#SELFDN" bind rules and confirm the target attribute cannot be set to an empty value, or add an explicit authmethod restriction to the ACI to prevent anonymous binds from satisfying the check. Where anonymous binds are not required, disabling anonymous access to the directory removes the attack surface entirely.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Red Hat CVSS v3 Score Explanation
Anonymous bind (empty DN) defeats any SELFDN ACI on an attribute permitted to hold an empty value, confirmed standalone in sandbox (no FreeIPA schema/plugins). AV:N/AC:L/PR:N/UI:N: reachable over LDAP, deterministic, zero credentials, no user interaction. S:U: impact confined to the right the vulnerable ACI itself grants. C:N/I:H/A:N: confirmed primitive is unauthorized write (ADD) of attacker-chosen content; no confidentiality or availability impact demonstrated. Impact assumes a realistic worst-case consuming ACI; RHDS ships no such ACI by default, so real-world severity is deployment-dependent.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data; Read Files or Directories
An attacker could bypass intended access restrictions to read sensitive data, either by reading the data directly from a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
Integrity
Technical Impact: Modify Application Data; Modify Files or Directories
An attacker could bypass intended access restrictions to modify sensitive data, either by writing the data directly to a data store that is not correctly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access Control
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism
An attacker could bypass intended access restrictions to gain privileges by modifying or reading critical data directly, or by accessing privileged functionality.
Confidentiality,Integrity,Availability
Technical Impact: Execute Unauthorized Code or Commands
An attacker could use elevated privileges to execute unauthorized commands or code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
An attacker could gain unauthorized access to resources on the system and excessively consume those resources, leading to a denial of service.
Acknowledgements
Red Hat would like to thank Gia Bui (yabeow) (Calif.io) for reporting this issue.
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