CVE-2017-16228 in Dulwich
Summary
by MITRE
Dulwich before 0.18.5, when an SSH subprocess is used, allows remote attackers to execute arbitrary commands via an ssh URL with an initial dash character in the hostname, a related issue to CVE-2017-9800, CVE-2017-12836, CVE-2017-12976, CVE-2017-1000116, and CVE-2017-1000117.
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Analysis
by VulDB Data Team • 01/05/2023
The vulnerability identified as CVE-2017-16228 represents a critical command injection flaw within the Dulwich Python library version 0.18.4 and earlier. This security issue specifically affects applications that utilize SSH subprocess functionality for Git operations, creating a pathway for remote attackers to execute arbitrary code on systems running vulnerable versions. The flaw stems from improper input validation when processing SSH URLs that contain an initial dash character in the hostname component, allowing malicious actors to inject additional command parameters that get passed directly to the underlying SSH subprocess.
The technical implementation of this vulnerability involves the manipulation of SSH URL parsing within the Dulwich library's Git protocol handling mechanisms. When a Git repository is accessed via SSH using a URL containing a hostname that begins with a dash character, the library fails to properly sanitize the input before constructing the command line arguments for the SSH subprocess. This improper sanitization creates a command injection vector where attacker-controlled data can be interpreted as additional command-line parameters, effectively bypassing normal security boundaries. The vulnerability is categorized under CWE-77 as a Command Injection, specifically manifesting as an issue in argument handling within subprocess execution contexts. The flaw operates at the intersection of input validation and subprocess management, where the library's failure to properly escape or quote command-line arguments creates an exploitable condition.
From an operational perspective, this vulnerability poses significant risks to organizations relying on Git-based workflows and version control systems that utilize the Dulwich library. Attackers can exploit this weakness to execute arbitrary commands with the privileges of the user running the Git operations, potentially leading to complete system compromise. The impact extends beyond simple code execution to include data exfiltration, privilege escalation, and persistence mechanisms that could allow attackers to maintain long-term access to affected systems. The vulnerability affects both development environments and production systems where Git repositories are accessed through SSH protocols, particularly impacting continuous integration pipelines, automated deployment systems, and collaborative development platforms that depend on secure Git operations.
The exploitation of this vulnerability aligns with several tactics outlined in the MITRE ATT&CK framework, specifically targeting techniques related to command execution and privilege escalation. Attackers can leverage this flaw to perform lateral movement within networks by executing commands on systems that have access to Git repositories, potentially accessing sensitive code repositories and configuration files. The vulnerability's relationship to other CVEs including CVE-2017-9800, CVE-2017-12836, CVE-2017-12976, CVE-2017-1000116, and CVE-2017-1000117 demonstrates a pattern of command injection issues affecting Git-related software components, indicating that similar vulnerabilities may exist in related systems. Organizations should prioritize immediate remediation by upgrading to Dulwich version 0.18.5 or later, implementing network-based restrictions on Git operations, and conducting thorough security assessments of systems that utilize SSH-based Git workflows. Additionally, organizations should consider implementing input validation at multiple layers, including network firewalls, proxy systems, and application-level controls to prevent exploitation of similar command injection vulnerabilities across their infrastructure.