A use-after-return vulnerability exists in the `named` server when handling DNS queries signed with SIG(0). Using a specially-crafted DNS request, an attacker may be able to cause an ACL to improperly (mis)match an IP address. In a default-allow ACL (denying only specific IP addresses), this may lead to unauthorized access. Default-deny ACLs should fail-secure.
This issue affects BIND 9 versions 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, and 9.20.9-S1 through 9.20.20-S1.
BIND 9 versions 9.18.0 through 9.18.46 and 9.18.11-S1 through 9.18.46-S1 are NOT affected.

Project Subscriptions

Vendors Products
Advisories

No advisories yet.

Fixes

Solution

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.21, 9.21.20, or 9.20.21-S1.


Workaround

No workarounds known.

History

Wed, 25 Mar 2026 15:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 25 Mar 2026 14:00:00 +0000

Type Values Removed Values Added
Description A use-after-return vulnerability exists in the `named` server when handling DNS queries signed with SIG(0). Using a specially-crafted DNS request, an attacker may be able to cause an ACL to improperly (mis)match an IP address. In a default-allow ACL (denying only specific IP addresses), this may lead to unauthorized access. Default-deny ACLs should fail-secure. This issue affects BIND 9 versions 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, and 9.20.9-S1 through 9.20.20-S1. BIND 9 versions 9.18.0 through 9.18.46 and 9.18.11-S1 through 9.18.46-S1 are NOT affected.
Title A stack use-after-return flaw in SIG(0) handling code may enable ACL bypass
First Time appeared Isc
Isc bind
Weaknesses CWE-305
CWE-562
CPEs cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
Vendors & Products Isc
Isc bind
References
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: isc

Published:

Updated: 2026-03-25T14:13:01.659Z

Reserved: 2026-03-05T12:50:58.915Z

Link: CVE-2026-3591

cve-icon Vulnrichment

Updated: 2026-03-25T14:12:54.940Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-03-25T14:16:37.297

Modified: 2026-03-25T15:41:33.977

Link: CVE-2026-3591

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses