Vulnerability 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 Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Isc | Bind | >= 9.20.0, < 9.20.21 |
Related Weaknesses (CWE)
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
FAQ
What is CVE-2026-3591?
CVE-2026-3591 is a vulnerability with a CVSS score of 5.4 (MEDIUM). 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...
How severe is CVE-2026-3591?
CVE-2026-3591 has been rated MEDIUM with a CVSS base score of 5.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-3591?
Check the references section above for vendor advisories and patch information. Affected products include: Isc Bind.