CVE-2021-26675
📋 TL;DR
This vulnerability allows network-adjacent attackers to execute arbitrary code via a stack-based buffer overflow in ConnMan's dnsproxy component. It affects systems running ConnMan before version 1.39, primarily Linux-based IoT devices, mobile devices, and embedded systems using this connection manager. Attackers must be on the same network segment as the vulnerable device.
💻 Affected Systems
- ConnMan (Connection Manager)
📦 What is this software?
Connman by Intel
Leap by Opensuse
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with root/system privileges leading to complete system compromise, lateral movement, and persistent backdoor installation.
Likely Case
Denial of service (crash of dnsproxy service) disrupting network connectivity, with potential for limited code execution depending on exploit sophistication.
If Mitigated
Service disruption only if exploit attempts are blocked by network segmentation or security controls.
🎯 Exploit Status
Exploit requires network adjacency and knowledge of target's DNS proxy service. Public references include technical analysis and proof-of-concept details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.39 and later
Vendor Advisory: https://lists.debian.org/debian-lts-announce/2021/02/msg00013.html
Restart Required: Yes
Instructions:
1. Update ConnMan to version 1.39 or later using your distribution's package manager. 2. For Debian/Ubuntu: sudo apt update && sudo apt upgrade connman. 3. For source installations: Download from git.kernel.org and compile. 4. Restart ConnMan service: sudo systemctl restart connman.service
🔧 Temporary Workarounds
Disable dnsproxy
linuxTemporarily disable the vulnerable dnsproxy component if DNS forwarding isn't required.
sudo systemctl stop connman-dnsproxy
sudo systemctl disable connman-dnsproxy
Network segmentation
allIsolate vulnerable devices to prevent network-adjacent attacks.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate vulnerable devices from untrusted networks
- Deploy network-based intrusion prevention systems (IPS) to detect and block exploit attempts
🔍 How to Verify
Check if Vulnerable:
Check ConnMan version: connmand --version or dpkg -l | grep connman. If version is below 1.39, system is vulnerable.Check Version:
connmand --version 2>/dev/null || dpkg -l | grep connman || rpm -q connmanVerify Fix Applied:
Verify version is 1.39 or higher: connmand --version. Check dnsproxy service status: systemctl status connman-dnsproxy.📡 Detection & Monitoring
Log Indicators:
- ConnMan/dnsproxy crash logs in systemd journal
- Abnormal DNS query patterns to dnsproxy
- Segmentation fault errors in /var/log/syslog
Network Indicators:
- Unusual DNS traffic to port 53 from unexpected sources
- DNS queries with malformed packets exceeding normal size
SIEM Query:
source="connman" AND ("segmentation fault" OR "buffer overflow" OR "crash")🔗 References
- https://bugzilla.suse.com/show_bug.cgi?id=1181751
- https://git.kernel.org/pub/scm/network/connman/connman.git/commit/?id=e4079a20f617a4b076af503f6e4e8b0304c9f2cb
- https://git.kernel.org/pub/scm/network/connman/connman.git/tree/ChangeLog
- https://kunnamon.io/tbone/
- https://lists.debian.org/debian-lts-announce/2021/02/msg00013.html
- https://security.gentoo.org/glsa/202107-29
- https://www.debian.org/security/2021/dsa-4847
- https://www.openwall.com/lists/oss-security/2021/02/08/2
- https://bugzilla.suse.com/show_bug.cgi?id=1181751
- https://git.kernel.org/pub/scm/network/connman/connman.git/commit/?id=e4079a20f617a4b076af503f6e4e8b0304c9f2cb
- https://git.kernel.org/pub/scm/network/connman/connman.git/tree/ChangeLog
- https://kunnamon.io/tbone/
- https://lists.debian.org/debian-lts-announce/2021/02/msg00013.html
- https://security.gentoo.org/glsa/202107-29
- https://www.debian.org/security/2021/dsa-4847
- https://www.openwall.com/lists/oss-security/2021/02/08/2
