What is CVE-2026-3591?

CVE-2026-3591 is a medium-severity vulnerability in Isc Bind, classified under Authentication Bypass by Primary Weakness. CVSS score: 5.4/10. Published 2026-03-25.

How severe is CVE-2026-3591?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Vulnerability in Isc Bind

CVE-2026-3591

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…

EPSS: 0.000 (8.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.

Affected products

Isc Bind
Isc Bind 9 — versions 9.20.0, 9.21.0, 9.20.9-S1

Weakness classification (CWE)

References

security-officer@isc.org (vendor-advisory, Vendor Advisory)
security-officer@isc.org (Patch, patch)
security-officer@isc.org (Patch, patch)

Frequently asked questions

What is CVE-2026-3591?: CVE-2026-3591 is a medium-severity vulnerability in Isc Bind, classified under Authentication Bypass by Primary Weakness. CVSS score: 5.4/10. Published 2026-03-25.
How severe is CVE-2026-3591?: Medium severity. CVSS v3 base score is 5.4 out of 10.