CVE-2016-8606
📋 TL;DR
CVE-2016-8606 is a critical vulnerability in GNU Guile's REPL server that allows remote code execution via HTTP inter-protocol attacks. Attackers can send specially crafted HTTP requests to the REPL server's listening port to execute arbitrary commands with the privileges of the Guile process. This affects systems running GNU Guile 2.0.12 with the REPL server enabled and exposed to network access.
💻 Affected Systems
- GNU Guile
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Fedora by Fedoraproject
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root privileges if Guile runs as root, allowing attackers to install malware, exfiltrate data, or pivot to other systems.
Likely Case
Remote code execution with the privileges of the Guile process, potentially leading to data theft, service disruption, or lateral movement within the network.
If Mitigated
Limited impact if the REPL server is not enabled or properly firewalled, though local exploitation might still be possible.
🎯 Exploit Status
The exploit involves sending HTTP requests to the REPL server port, which is relatively straightforward. Public proof-of-concept code exists in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.0.13 and later
Vendor Advisory: https://lists.gnu.org/archive/html/guile-devel/2016-10/msg00000.html
Restart Required: Yes
Instructions:
1. Update GNU Guile to version 2.0.13 or later using your package manager. 2. For source installations: download latest source from ftp.gnu.org/gnu/guile/, compile and install. 3. Restart any services using Guile.
🔧 Temporary Workarounds
Disable REPL Server
linuxRemove or disable the --listen option from Guile startup configurations
Check startup scripts and configuration files for '--listen' arguments and remove them
Network Isolation
linuxBlock network access to the REPL server port using firewall rules
iptables -A INPUT -p tcp --dport [REPL_PORT] -j DROP
Replace [REPL_PORT] with actual port number
🧯 If You Can't Patch
- Disable the REPL server entirely by removing --listen from all configurations
- Implement strict network segmentation and firewall rules to block all access to the REPL server port
🔍 How to Verify
Check if Vulnerable:
Check if Guile version is 2.0.12 and if any processes are running with --listen option: ps aux | grep guile | grep listenCheck Version:
guile --version | head -1Verify Fix Applied:
Verify Guile version is 2.0.13 or higher: guile --version📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to non-standard ports
- Guile process spawning unexpected child processes
- Errors in Guile logs related to REPL server
Network Indicators:
- HTTP traffic to ports typically used by Guile REPL (default 37146)
- Unusual outbound connections from Guile processes
SIEM Query:
source="*guile*" AND ("--listen" OR "REPL" OR port=37146)🔗 References
- http://www.openwall.com/lists/oss-security/2016/10/12/2
- http://www.securityfocus.com/bid/93514
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6QTAGSDCTYXTABAA77BQJGNKOOBRV4DK/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FNVE5N24FLWDYBQ3LAFMF6BFCWKDO7VM/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UJP5S36GTXMDEBXWF6LKKV76DSLNQG44/
- http://www.openwall.com/lists/oss-security/2016/10/12/2
- http://www.securityfocus.com/bid/93514
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6QTAGSDCTYXTABAA77BQJGNKOOBRV4DK/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FNVE5N24FLWDYBQ3LAFMF6BFCWKDO7VM/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UJP5S36GTXMDEBXWF6LKKV76DSLNQG44/
