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Vulnerability record · CVE-2026-3591 · published 25 March 2026

CVE-2026-3591: Isc bind vulnerability

Isc · Bind

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.

5.4 CVSS 3.1 Medium EPSS 0.32% · top 77.0% CWE-305 · CWE-305CWE-562 · CWE-562
5.4CVSS 3.1 base score
0.32%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://downloads.isc.org/isc/bind9/9.20.21 Patch
https://downloads.isc.org/isc/bind9/9.21.20 Patch
https://kb.isc.org/docs/cve-2026-3591 Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2008-0122Isc bind vulnerabilityOff-by-one error in the inet_network function in libbind in ISC BIND 9.4.2 and earlier, as used in libc in FreeBSD 6.2 through 7.0-PRERELEASE, allows…EPSS 12%10.0CVE-2001-0010Isc bind vulnerabilityBuffer overflow in transaction signature (TSIG) handling code in BIND 8 allows remote attackers to gain root privileges.EPSS 32%10.0CVE-2001-0011Isc bind vulnerabilityBuffer overflow in nslookupComplain function in BIND 4 allows remote attackers to gain root privileges.EPSS 7.7%10.0CVE-2001-0013Isc bind vulnerabilityFormat string vulnerability in nslookupComplain function in BIND 4 allows remote attackers to gain root privileges.EPSS 11%10.0CVE-2000-1029Isc bind vulnerabilityBuffer overflow in host command allows a remote attacker to execute arbitrary commands via a long response to an AXFR query.EPSS 14%10.0CVE-1999-0837Isc bind vulnerabilityDenial of service in BIND by improperly closing TCP sessions via so_linger.EPSS 2.7%10.0CVE-1999-0009Data general dg ux vulnerabilityInverse query buffer overflow in BIND 4.9 and BIND 8 Releases.EPSS 29%9.8CVE-2026-3593Isc bind use after free vulnerabilityA use-after-free vulnerability exists within the DNS-over-HTTPS implementation. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 thr…EPSS 1.1%

Source: NIST National Vulnerability Database (record CVE-2026-3591), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.