Strix
26.1K

CVE-2026-3591

MEDIUMCVSS 5.4/10EPSS 0.36%

Last modified

CVE-2026-3591 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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. EPSS estimates a 0.36% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
5.4/10

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

EPSS Probability
0.36%

27.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
IscBind>= 9.20.0, < 9.20.21
IscBind>= 9.21.0, < 9.21.20

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is 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-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.
How severe is CVE-2026-3591?
CVE-2026-3591 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.36% probability of exploitation in the next 30 days.
How do I fix CVE-2026-3591?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-3591?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST