CVE-2026-11789
Description
A flaw was found in 389 Directory Server. The SMD5 password storage plugin performs unsigned integer underflow when computing salt length from a crafted password hash shorter than 16 bytes, causing a buffer over-read that crashes the LDAP server during authentication.
Statement
Red Hat rates this issue as Moderate impact. The SMD5 password storage plugin in 389-ds-base underflows when computing salt length from a stored hash shorter than 16 bytes, causing the server to crash during LDAP BIND. NVD rates 6.5 (PR:L); Red Hat rates 4.9 (PR:H) because planting the crafted hash requires Directory Manager privileges or the non-default nsslapd-allow-hashed-passwords setting. Once planted, the crash re-triggers on every bind to the poisoned account until the hash is removed offline. This is a missed variant of CVE-2024-5953, which patched md5_pwd.c and pbkdf2_pwd.c but not smd5_pwd.c.
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. Migrate stored passwords from {SMD5} to {PBKDF2_SHA256} to eliminate the vulnerable code path for existing accounts.
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 | 6.5 | 4.9 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | High | Low | High |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:L/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
Missed variant of CVE-2024-5953 — smd5_pwd.c not patched. PR:H — Directory Manager must plant crafted hash.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Instability
This weakness will generally lead to undefined behavior and therefore crashes. In the case of overflows involving loop index variables, the likelihood of infinite loops is also high.
Integrity
Technical Impact: Modify Memory
If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the wrap around results in other conditions such as buffer overflows, further memory corruption may occur.
Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism
This weakness can sometimes trigger buffer overflows which can be used to execute arbitrary code. This is usually outside the scope of a program's implicit security policy.
Acknowledgements
This issue was discovered by Ian Murphy (Red Hat).
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