VulnerabilityAnalyzed

CVE-2026-3591

A use-after-return vulnerability exists in the `named` server when handling DNS queries signed with SIG(0).

MEDIUM 5.4EPSS 0.36%

Does this matter?

Lower severity and a low EPSS score (0.36%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 5.4 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
EPSS: 0.36% probability · 29th percentile
CISA KEV: Not listed
Weakness: CWE-305, CWE-562
Affected: isc/bind
Source: security-officer@isc.org

References

https://downloads.isc.org/isc/bind9/9.20.21Patch
https://downloads.isc.org/isc/bind9/9.21.20Patch
https://kb.isc.org/docs/cve-2026-3591Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.