CVE-2026-3591
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert: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 Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.4 | N/A | 5.4 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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