CVE-2026-16560
Description
A heap-buffer-overflow flaw was found in Directory Server (389-ds-base). When a DN contains a legacy-quoted value, the server won't close the heap allocation allowing another call to refer to the same memory pointer causing a denial of service or an arbitrary memory write operation.
Statement
Red-hat rates this vulnerability as Moderate impact. The function can allow an unauthenticated attacker to send malformed DN requests and trigger the bug. Denial of service is more reliably observed when heap debugging is enabled (for example AddressSanitizer or MALLOC_CHECK_=3), or depending on heap layout and subsequent memory allocator activity. For this reason Red Hat rates availability impact as Low (A:L) rather than High. There is no configuration switch to disable DN normalization for client-supplied DNs.
Mitigation
Denial of service is more reliably observed
when heap debugging is enabled (for example AddressSanitizer or MALLOC_CHECK_=3),
or depending on heap layout and subsequent memory allocator activity. For this
reason Red Hat rates availability impact as Low (A:L) rather than High.
There is no configuration switch to disable DN normalization for client-supplied DNs.
The vulnerable code path is present in all currently supported 389-ds-base versions
that ship the quoted-RDN parsing logic in dn.c.
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 | 5.3 | N/A | 5.3 |
| 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 | None | N/A | None |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability,Access Control
Technical Impact: Modify Memory; Read Memory; Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity; Bypass Protection Mechanism; Other
Acknowledgements
Red Hat would like to thank Denis Rastyogin (ALT Linux) for reporting this issue.
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