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Fencer Intel
medium 5.4

CVE-2026-3591 json

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

published 7mo ago modified 4mo 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

Is CVE-2026-3591 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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
7mo ago

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-09).

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 Intel 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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.