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Fencer Vulns
medium 5.4

CVE-2026-3591 json

A stack use-after-return flaw in SIG(0) handling code may enable ACL bypass

published 2026-03-25 7 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-15413

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

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.

Patch / fix

  • ISC BIND 9 9.18.0, 9.18.11-S1
  • bind9 Debian 13 1:9.20.21-1~deb13u1
  • bind9 Debian 14 1:9.20.21-1

debian advisories DEBIAN-CVE-2026-3591

  • bind9 Ubuntu 25.10 1:9.20.11-1ubuntu2.2

ubuntu advisories UBUNTU-CVE-2026-3591

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • bind hummingbird 1 9.18.48-1.hum1
  • bind-libs hummingbird 1 9.18.48-1.hum1
  • bind-utils hummingbird 1 9.18.48-1.hum1
  • bind-chroot hummingbird 1 9.18.48-1.hum1
  • bind-dnssec-utils hummingbird 1 9.18.48-1.hum1

red hat advisories RHSA-2026:6935

  • bind SLES for SAP applications 16.0, SLES 16.0 9.20.21-160000.1.1
  • bind SLE Module for Server Applications 15 SP7, SLE Module for Basesystem 15 SP7 9.20.21-150700.3.18.1

suse advisories SUSE-SU-2026:21204-1SUSE-SU-2026:1351-1

  • bind openSUSE Leap 16.0 9.20.21-160000.1.1
  • bind openSUSE Tumbleweed 9.20.21-1.1

opensuse advisories openSUSE-SU-2026:20550-1openSUSE-SU-2026:10448-1

  • bind Alpine 3.24, Alpine 3.23, Alpine 3.22 9.20.21-r0

alpine advisories ALPINE-CVE-2026-3591

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • bind Azure Linux 3.0 9.20.21-1

azure linux advisories AZL-80987

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-3591 updated cvss 5.4

bind: BIND: Unauthorized access due to use-after-return vulnerability in DNS query handling

  • Red Hat Enterprise Linux 10 bind
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images bind 9.18.48-1.hum1, bind-libs 9.18.48-1.hum1, bind-utils 9.18.48-1.hum1, bind-chroot 9.18.48-1.hum1, bind-dnssec-utils 9.18.48-1.hum1
    fixed: vendor fix RHSA-2026:6935
  • Red Hat Enterprise Linux 6 bind, bind-sdb, bind-libs, bind-utils, bind-chroot Red Hat Enterprise Linux 7 bind, bind-sdb, bind-libs, bind-utils, bind-chroot, bind-pkcs11, +6 more Red Hat Enterprise Linux 8 bind, bind-sdb, bind9.16, bind-libs, bind-utils, bind-chroot, +14 more Red Hat Enterprise Linux 9 bind, dhcp, bind9.18, bind-libs, bind-utils, dhcp-relay, +11 more Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected products

  • ISC BIND 9

Classification

Weakness
  • CWE-562 Return of Stack Variable Address
  • CWE-305 Authentication Bypass by Primary Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.