Medium [CVE-2026-16560] heap-buffer-overflow in rdn_av_swap on quoted multivalued RDN
This medium-severity Red Hat Linux advisory covers CVE-2026-16560 affecting Red Hat Directory Server 11, Red Hat Directory Server 12, Red Hat Directory Server 13.
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Summary
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.
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. There is no configuration switch to disable DN normalization for client-supplied DNs.
Red Hat severity: Moderate — CVSS 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L). Weakness: CWE-1220.
Affected Red Hat products: Red Hat Directory Server 11; Red Hat Directory Server 12; Red Hat Directory Server 13; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9. Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: 389-ds-base.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
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