CVE-2024-1488: Unbound Privilege Escalation Vulnerability

CVE-2024-1488 Overview

A vulnerability was discovered in Unbound DNS resolver due to incorrect default permissions, allowing any process outside the unbound group to modify the unbound runtime configuration. If a process can connect over localhost to port 8953, it can alter the configuration of unbound.service. This flaw allows an unprivileged attacker to manipulate a running instance, potentially altering forwarders, allowing them to track all queries forwarded by the local resolver, and, in some cases, disrupting resolving altogether.

Critical Impact

Unprivileged local attackers can modify DNS resolver configuration, enabling DNS query tracking and potential DNS resolution disruption across the affected system.

Affected Products

• Fedoraproject Unbound
• Red Hat Enterprise Linux 8.0 and 9.0 (including EUS variants)
• Red Hat CodeReady Linux Builder 9.0 and 9.2
• Red Hat Enterprise Linux for ARM64, IBM Z Systems, and Power Little Endian architectures
• Red Hat Enterprise Linux Server AUS, TUS, and SAP Solutions variants

Discovery Timeline

• February 15, 2024 - CVE-2024-1488 published to NVD
• January 30, 2025 - Last updated in NVD database

Technical Details for CVE-2024-1488

Vulnerability Analysis

This vulnerability stems from CWE-276 (Incorrect Default Permissions) in the Unbound DNS resolver's control interface configuration. Unbound provides a remote control interface on localhost port 8953 that allows administrators to modify the resolver's runtime configuration without restarting the service. The vulnerability occurs because the default permissions on this control interface are insufficiently restrictive, allowing processes that are not members of the unbound group to connect and issue configuration commands.

The attack requires local access to the system, making it a local privilege escalation and configuration manipulation vulnerability. Once an attacker gains access to any user account on the system, they can connect to the Unbound control socket and modify critical DNS resolution settings including forwarder configurations, access control lists, and other runtime parameters.

Root Cause

The root cause is improper access control configuration for the Unbound remote control interface. The default installation does not properly restrict which local users or processes can communicate with the unbound-control interface on port 8953. This allows any local process with network access to localhost to interact with the DNS resolver's management interface, bypassing the intended restriction that only processes running as part of the unbound group should have such access.

Attack Vector

An attacker who has compromised a low-privilege account on a system running Unbound can exploit this vulnerability through the following mechanism:

1. The attacker identifies that Unbound is running and the remote control interface is enabled on localhost:8953
2. Without needing any special permissions, the attacker connects to the control interface
3. The attacker issues configuration commands to modify DNS forwarders to point to a malicious DNS server under their control
4. All DNS queries from the local resolver are now forwarded to the attacker's server, enabling DNS query logging, response manipulation, or complete DNS resolution disruption

The vulnerability can be exploited to perform DNS hijacking at the local resolver level, intercept sensitive DNS queries, or cause denial of service by disrupting DNS resolution for the entire system.

Detection Methods for CVE-2024-1488

Indicators of Compromise

• Unexpected connections to localhost port 8953 from processes outside the unbound group
• Modifications to Unbound forwarder configurations that were not authorized by administrators
• DNS queries being forwarded to unknown or suspicious external DNS servers
• Unexplained changes to unbound.conf runtime settings or access control configurations

Detection Strategies

• Monitor network connections to localhost:8953 and alert on connections from unexpected process IDs or user contexts
• Implement file integrity monitoring on Unbound configuration files and the control socket permissions
• Use audit logging to track unbound-control command executions and configuration changes
• Deploy host-based intrusion detection to identify unauthorized attempts to interact with the Unbound control interface

Monitoring Recommendations

• Configure system auditing to log all access attempts to /var/run/unbound/ directory and the control socket
• Establish baselines for legitimate Unbound configuration and alert on deviations
• Monitor DNS query patterns for unusual forwarding behavior or queries to unexpected resolvers
• Implement SentinelOne endpoint protection to detect suspicious local network activity and unauthorized process interactions

How to Mitigate CVE-2024-1488

Immediate Actions Required

• Apply the latest security patches from your distribution vendor immediately
• Verify and restrict permissions on the Unbound control interface socket to the unbound group only
• Disable the remote control interface if not required by setting remote-control: no in unbound.conf
• Audit current Unbound configuration for any unauthorized modifications to forwarders or access controls

Patch Information

Red Hat has released multiple security advisories addressing this vulnerability across their product portfolio. Administrators should apply the appropriate patches based on their specific Red Hat Enterprise Linux version:

• Red Hat Security Advisory RHSA-2024:1750
• Red Hat Security Advisory RHSA-2024:1751
• Red Hat Security Advisory RHSA-2024:1780
• Red Hat Security Advisory RHSA-2024:1801
• Red Hat Security Advisory RHSA-2024:2587
• Red Hat Security Advisory RHSA-2025:0837

For detailed vulnerability information, see the Red Hat CVE-2024-1488 Overview and Red Hat Bugzilla Report #2264183.

Workarounds

• Disable the remote control interface entirely by setting remote-control: control-enable: no in the Unbound configuration
• Restrict socket permissions manually using chmod and chown to ensure only the unbound user and group can access the control socket
• Implement firewall rules to block access to port 8953 from unauthorized processes as an additional layer of defense
• Consider running Unbound in a container or namespace to provide additional isolation from other system processes

# Configuration example - Disable remote control interface
# Add or modify in /etc/unbound/unbound.conf:
remote-control:
    control-enable: no

# Or restrict permissions on the control socket
sudo chmod 660 /var/run/unbound/unbound.sock
sudo chown unbound:unbound /var/run/unbound/unbound.sock

# Restart Unbound to apply changes
sudo systemctl restart unbound