CVE-2026-3591

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. Limited direct impact.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-03-25 14:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 10:43 UTC Last updatedMost recent change to the record

Details

Published

2026-03-25 14:16 UTC

Last modified

2026-06-17 10:43 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-305

Record status

Analyzed

Affected

• Isc Bind < 9.20.21
• Isc Bind < 9.21.20

Attack profile CVSS 3.1 · 5.4

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None