Is CVE-2026-3591 in the CISA KEV catalog?

No. CVE-2026-3591 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-3591?

CVE-2026-3591 has a CVSS v3 base score of 5.4 (Moderate).

What is the EPSS score for CVE-2026-3591?

CVE-2026-3591 has an EPSS score of 0.36% (28th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-3591?

Upgrade bind9 on debian 13 to 1:9.20.21-1~deb13u1 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2026-3591

MEDIUM

5.4

CVSS v3

NVD

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.

CWE-305 CWE-562

How to fix

Remediation Available

bind9Debian

Fixed in:1:9.20.21-1~deb13u1CVE-2026-3591

Fixed in:1:9.20.21-1CVE-2026-3591

bind9Ubuntu

Fixed in:1:9.18.39-0ubuntu0.22.04.3USN-8124-1

Fixed in:1:9.18.39-0ubuntu0.24.04.3USN-8124-1

Fixed in:1:9.20.11-1ubuntu2.2USN-8124-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Exploit Intelligence

0.36%probability of exploitation in 30 days

28thpercentile

Low risk: more likely to be exploited than 28% of all known CVEs.

References

Patch2

Vendor Advisory1

kb.isc.org

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-21.