CVE-2026-11788
Description
A flaw was found in 389 Directory Server. The dereference control plugin does not check for allocation failure before using a BER structure, allowing an unauthenticated remote attacker to crash the LDAP server when the system is under memory pressure.
Statement
Red Hat rates this issue as Moderate impact. The dereference control plugin in 389-ds-base does not check whether ber_init() succeeded before using the BER structure. If allocation fails, an LDAP search carrying the deref control can crash ns-slapd. The deref plugin is enabled by default, and anonymous clients can send the control when anonymous access is allowed. NVD rates this 7.5 (AC:L); Red Hat rates 5.9 (AC:H) because the NULL return from ber_init() occurs when memory allocation fails, not from a crafted control payload alone—a well-formed deref search on a server with normal free memory does not trigger the crash. Natural OOM was not demonstrated end-to-end without fault injection. Disabling the deref plugin removes the vulnerable code path entirely.
Mitigation
Disable the deref plugin (most effective): dsconf <instance> plugin deref disable; systemctl restart dirsrv@<instance>. Disable anonymous access (nsslapd-allow-anonymous-access=off) to raise the bar from pre-auth to authenticated exploitation. Configure memory limits as defense-in-depth: set nsslapd-maxbersize and nsslapd-conntablesize, and deploy in a cgroup with memory limits.
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 | 5.9 | 7.5 | 5.9 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | None | None | None |
| 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:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
AC:H — requires memory pressure for ber_init() NULL. PR:N — anonymous deref search sufficient. Crash confirmed Fedora 42 + CentOS 7.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
Acknowledgements
This issue was discovered by Ian Murphy (Red Hat).
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