CVE-2025-32743 Overview
A critical memory corruption vulnerability has been identified in ConnMan through version 1.44. The flaw exists in the ns_resolv function within dnsproxy.c, where the lookup string can be NULL or an empty string when the TC (Truncated) bit is set in a DNS response. This condition leads to incorrect length calculations and improper memcpy operations, enabling attackers to cause a denial of service through application crashes or potentially achieve arbitrary code execution.
Critical Impact
This 0-click vulnerability in ConnMan's DNS proxy can be exploited remotely without user interaction, potentially allowing attackers to crash network services or execute arbitrary code on affected systems.
Affected Products
- ConnMan through version 1.44
- ConnMan version 1.43
- Systems utilizing ConnMan's DNS proxy functionality
Discovery Timeline
- April 10, 2025 - CVE-2025-32743 published to NVD
- April 11, 2025 - Last updated in NVD database
Technical Details for CVE-2025-32743
Vulnerability Analysis
The vulnerability resides in ConnMan's DNS proxy implementation, specifically in the ns_resolv function located in dnsproxy.c. When processing DNS responses with the TC (Truncated) bit set, the code fails to properly validate the lookup string before performing memory operations. The lookup string can become NULL or empty under these specific conditions, but subsequent code assumes a valid string is present.
This improper condition handling (CWE-392) results in incorrect length calculations being passed to memcpy operations. When the length calculation is performed on a NULL or empty lookup string, the resulting value can cause buffer operations to read or write memory outside the intended boundaries, leading to memory corruption.
The network-accessible nature of this vulnerability means attackers can trigger it remotely by sending specially crafted DNS responses. The attack requires no user interaction (0-click), making it particularly dangerous for systems exposed to untrusted network traffic.
Root Cause
The root cause is improper condition handling in the DNS response processing logic. When a DNS response arrives with the TC (Truncated) bit set, the code path in ns_resolv can result in a NULL or empty lookup string. The function fails to validate this condition before using the lookup value in subsequent length calculations and memory copy operations.
Specifically, at line 1688 in dnsproxy.c, the code does not adequately check whether the lookup string is valid before proceeding with operations that depend on a non-null, non-empty value. This oversight allows corrupted state to propagate through the memcpy calls, causing memory corruption.
Attack Vector
The attack vector is network-based and requires no authentication or user interaction. An attacker positioned to intercept or inject DNS traffic can exploit this vulnerability by:
- Intercepting legitimate DNS queries from a ConnMan-managed system
- Crafting a malicious DNS response with the TC (Truncated) bit set
- Manipulating the response to trigger the NULL or empty lookup string condition
- Sending the crafted response to cause memory corruption in the target's DNS proxy
The vulnerability mechanism involves DNS response handling where truncated responses trigger improper string processing. When the TC bit indicates truncation, the ns_resolv function may receive a NULL or empty lookup parameter, which then cascades into length miscalculations during memcpy operations. Technical details are available in the 0-click Vulnerability Report and the ConnMan source code reference.
Detection Methods for CVE-2025-32743
Indicators of Compromise
- ConnMan daemon crashes or unexpected restarts, particularly during DNS resolution operations
- Segmentation fault messages in system logs referencing dnsproxy.c or ns_resolv
- Unusual DNS traffic patterns, especially responses with the TC (Truncated) bit set
- Memory corruption indicators in process dumps related to the connmand process
Detection Strategies
- Monitor for abnormal terminations of the connmand process and configure automatic alerting
- Implement network traffic analysis to detect malformed DNS responses with suspicious TC bit patterns
- Deploy intrusion detection signatures that identify DNS response anomalies targeting ConnMan systems
- Enable core dump collection for ConnMan processes to facilitate forensic analysis after crashes
Monitoring Recommendations
- Configure syslog monitoring for ConnMan-related crash events and segmentation faults
- Implement DNS traffic baseline monitoring to identify unusual response patterns
- Set up process health monitoring for connmand with automatic restart alerting
- Deploy network sensors capable of deep packet inspection on DNS traffic
How to Mitigate CVE-2025-32743
Immediate Actions Required
- Identify all systems running ConnMan version 1.44 or earlier in your environment
- Evaluate exposure by determining which systems process untrusted DNS traffic
- Consider disabling ConnMan's DNS proxy functionality where not strictly required
- Implement network-level controls to filter potentially malicious DNS responses at perimeter devices
Patch Information
No official vendor patch information was available at the time of this analysis. Organizations should monitor the ConnMan Git repository for security updates addressing this vulnerability. When a patch becomes available, prioritize deployment on internet-facing and critical systems.
Workarounds
- Configure firewall rules to restrict DNS traffic to trusted resolvers only
- Implement DNS-over-HTTPS or DNS-over-TLS to encrypt and validate DNS traffic
- Deploy a separate DNS resolver in front of ConnMan to pre-validate responses
- Consider using alternative network management solutions on critical systems until a patch is available
# Configuration example: Restrict DNS traffic to trusted resolver only
# Add to iptables rules to limit DNS resolution sources
iptables -A OUTPUT -p udp --dport 53 -d <trusted_dns_ip> -j ACCEPT
iptables -A OUTPUT -p udp --dport 53 -j DROP
iptables -A INPUT -p udp --sport 53 -s <trusted_dns_ip> -j ACCEPT
iptables -A INPUT -p udp --sport 53 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
