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5.4 Medium

CVE-2026-3591 A use-after-return vulnerability exists in the `named` server when handling DNS queries signed with SIG(0)

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.

Affected products and versions

Product Affected versions Fixed in
BIND 9 9.21 9.21.0 → 9.21.19 No fix stated
BIND 9 9.20 9.20.0 → 9.20.20 No fix stated
BIND 9 9.18 earliest → < 9.18.0 9.18.0
The 87 CVEs of BIND 9 →
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