CVE-2026-3591

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Last Modified: UTC

Moderate Moderate Impact What does this mean?
5.4 CVSS v3 Base Score

Description

A flaw was found in BIND, specifically in the named server's handling of DNS queries signed with SIG(0). A remote attacker could exploit this use-after-return vulnerability by sending a specially-crafted DNS request. This could cause an Access Control List (ACL) to improperly match an IP address, potentially leading to unauthorized access to resources.

Statement

This vulnerability has a Moderate impact. A use-after-return flaw in the named server of bind9 allows a remote attacker to send a specially-crafted DNS request signed with SIG(0). This can lead to improper Access Control List (ACL) matching, potentially granting unauthorized access to resources. Red Hat Enterprise Linux 8 and 9 ship with BIND versions 9.16 and 9.18 respectively, which are not affected by this flaw. Red Hat Enterprise Linux 10 is affected.

Mitigation

Restrict network access to the `named` service to trusted clients and networks. Configure firewall rules to limit inbound connections to the DNS service port (UDP/TCP 53). For example, using `firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<TRUSTED_IP_RANGE>" port port="53" protocol="udp" accept'` and `firewall-cmd --reload`. This action may impact DNS resolution for clients outside the specified trusted networks. A service reload or restart may be required for changes to take effect.

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2026-3591

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2026-3591

Content from downloads.isc.org is not included.https://downloads.isc.org/isc/bind9/9.20.21

Content from downloads.isc.org is not included.https://downloads.isc.org/isc/bind9/9.21.20

Content from kb.isc.org is not included.https://kb.isc.org/docs/cve-2026-3591

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Enterprise Linux 10 bind Fix deferred
Red Hat Enterprise Linux 6 bind Not affected
Red Hat Enterprise Linux 7 bind Not affected
Red Hat Enterprise Linux 8 bind Not affected
Red Hat Enterprise Linux 8 bind9.16 Not affected
Red Hat Enterprise Linux 9 bind Not affected
Red Hat Enterprise Linux 9 bind9.18 Not affected
Red Hat Enterprise Linux 9 dhcp Not affected
Red Hat Hardened Images bind-main Fixed RHSA-2026:6935
Red Hat OpenShift Container Platform 4 rhcos Not affected
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 5.4
Attack Vector Network
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality Impact Low
Integrity Impact Low
Availability Impact None

CVSS v3 Vector

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

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.

My product is listed as "Out of Support Scope". What does this mean?

 When a product is listed as "Out of Support Scope", it means a vulnerability with the impact level assigned to this CVE is no longer covered by its current support lifecycle phase. The product has been identified to contain the impacted component, but analysis to determine whether it is affected or not by this vulnerability was not performed. The product should be assumed to be affected. Customers are advised to apply any mitigation options documented on this page, consider removing or disabling the impacted component, or upgrade to a supported version of the product that has an update available.