How severe is CVE-2026-3591?

CVE-2026-3591 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-3591 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3591?

CVE-2026-3591 affects Isc Bind. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-3591?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-3591 have an EU (EUVD) identifier?

Yes. CVE-2026-3591 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-15413.

When was CVE-2026-3591 published?

CVE-2026-3591 was published on 2026-03-25 and last updated on 2026-06-17.

CVE-2026-3591

CVE-2026-3591 is a medium-severity vulnerability in Isc Bind with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-305.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
EPSS exploit prediction: 0% (28th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-15413
Weakness: CWE-305
Affected product: Isc Bind
Published: 2026-03-25
Last modified: 2026-06-17

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.

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 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-3591 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3591?: CVE-2026-3591 affects Isc Bind. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-3591?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-3591 have an EU (EUVD) identifier?: Yes. CVE-2026-3591 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-15413.
When was CVE-2026-3591 published?: CVE-2026-3591 was published on 2026-03-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*

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