CVE-2026-11790
Description
A flaw was found in 389 Directory Server. The PBKDF2-SHA256 password storage plugin does not enforce an upper bound on the iteration count extracted from stored password hashes. A privileged attacker who can modify a user's password hash can cause excessive CPU consumption during authentication, resulting in denial of service.
Statement
Red Hat rates this issue as Moderate impact. The PBKDF2-SHA256 password storage plugin in 389-ds-base accepts unbounded iteration counts from stored password hashes. An attacker with Directory Manager access can plant a hash with extreme iterations; subsequent BIND operations hang worker threads for hours, enabling persistent denial of service. The poisoned hash persists in the database and re-triggers on every bind, so recovery requires Directory Manager access to replace the hash. This is distinct from CVE-2024-5953, which added hash length checks but not an iteration cap.
Mitigation
Disable nsslapd-allow-hashed-passwords (default: off) to prevent non-DM users from setting pre-hashed passwords. Restrict Directory Manager credentials; limit DM access to management networks and audit DM operations via nsslapd-auditlog. Monitor for suspicious userPassword modifications (unusual hash schemes or large base64 payloads). Monitor for unusually long bind operations to the same account, which may indicate a poisoned PBKDF2 hash.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.9 | N/A | 4.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | High | N/A | High |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
PR:H — attacker must plant crafted hash via Directory Manager. Persistent DoS: hash survives in DB and re-triggers on every bind.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
Acknowledgements
This issue was discovered by Ian Murphy (Red Hat).
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