CVE-2016-8606 in Guile
Summary
by MITRE
The REPL server (--listen) in GNU Guile 2.0.12 allows an attacker to execute arbitrary code via an HTTP inter-protocol attack.
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Analysis
by VulDB Data Team • 10/28/2022
The vulnerability identified as CVE-2016-8606 affects GNU Guile 2.0.12's Read-Eval-Print Loop (REPL) server functionality when operated in listening mode. This represents a critical security flaw that enables remote code execution through a specific type of HTTP inter-protocol attack vector. The vulnerability exists within the server's handling of incoming HTTP requests and demonstrates how improper input validation can lead to arbitrary code execution in a network service context.
The technical implementation of this vulnerability stems from insufficient sanitization of HTTP protocol interactions within the REPL server component. When GNU Guile operates in listen mode, it accepts incoming connections and processes HTTP requests through its embedded server. The flaw occurs during the parsing and interpretation of HTTP protocol elements, where attacker-controlled input can be manipulated to inject and execute malicious code within the running Guile process. This type of vulnerability aligns with CWE-74, which describes improper neutralization of special elements used in data queries, and CWE-94, which covers improper control of generation of code, commonly known as code injection vulnerabilities.
The operational impact of this vulnerability is severe and far-reaching within systems that utilize GNU Guile's REPL server functionality. An attacker can leverage this vulnerability to execute arbitrary commands on the target system with the privileges of the Guile process, potentially leading to complete system compromise. The attack requires minimal prerequisites since the vulnerability is present when the REPL server is actively listening, making it particularly dangerous in production environments where such services might be exposed to untrusted networks. The vulnerability can be exploited remotely without requiring authentication, making it especially concerning for systems where the REPL server is configured to accept connections from external hosts.
Systems at risk include any deployment of GNU Guile 2.0.12 where the --listen option is enabled, particularly in development environments or applications that expose the REPL server to network traffic. The vulnerability is particularly dangerous in containerized environments or cloud deployments where such services might be inadvertently exposed. Organizations using Guile for scripting or embedded application development should assess their configurations to ensure that REPL servers are not running in listening mode unless absolutely necessary. The attack pattern follows typical remote code execution methodologies described in the MITRE ATT&CK framework under T1059 for command and script injection, where adversaries leverage service vulnerabilities to execute malicious code on target systems.
Mitigation strategies for this vulnerability include upgrading to GNU Guile versions that contain patches for this issue, which were released after the vulnerability disclosure. Administrators should disable the --listen option when it is not required, or ensure that the REPL server is properly firewalled and restricted to trusted networks only. Network segmentation and access controls should be implemented to prevent unauthorized access to systems running vulnerable Guile versions. Additionally, monitoring for unusual network traffic patterns or unexpected command executions on systems running Guile services can help detect exploitation attempts. Security teams should also consider implementing runtime application self-protection measures and regularly auditing system configurations to prevent accidental exposure of vulnerable services. The patching process should be prioritized in environments where the REPL server functionality is actively used in production or development environments.