CVE-2019-5152 in shadowsocks-libev
Summary
by MITRE
An exploitable information disclosure vulnerability exists in the network packet handling functionality of Shadowsocks-libev 3.3.2. When utilizing a Stream Cipher, a specially crafted set of network packets can cause an outbound connection from the server, resulting in information disclosure. An attacker can send arbitrary packets to trigger this vulnerability.
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Analysis
by VulDB Data Team • 03/07/2025
The vulnerability identified as CVE-2019-5152 represents a critical information disclosure flaw within the Shadowsocks-libev 3.3.2 implementation that specifically affects the network packet handling mechanisms. This vulnerability resides in the stream cipher functionality of the shadowsocks-libev library, which is widely used for secure network communication and proxy services. The flaw manifests when the system processes specially crafted network packets that trigger unexpected behavior in the outbound connection handling, creating a vector for unauthorized information disclosure. This vulnerability is particularly concerning as it allows remote attackers to exploit the system without requiring authentication or prior access to the network infrastructure.
The technical implementation of this vulnerability stems from improper handling of network packet structures within the stream cipher processing module. When shadowsocks-libev encounters malformed or specially crafted packets during the stream cipher encryption process, the system's packet parsing logic fails to properly validate incoming data before establishing outbound connections. This processing error creates a scenario where information that should remain confidential becomes accessible through the unintended outbound communication channels. The flaw specifically impacts the way the system manages packet headers and payload structures, particularly when dealing with stream ciphers that do not maintain strict packet boundaries. According to CWE classification, this vulnerability maps to CWE-20: Improper Input Validation, as the system fails to adequately validate packet structures before processing them through the cryptographic pipeline.
The operational impact of CVE-2019-5152 extends beyond simple information disclosure to potentially compromise the entire security posture of systems utilizing vulnerable shadowsocks-libev implementations. Attackers can leverage this vulnerability by sending carefully constructed packets that trigger the information disclosure behavior, potentially exposing sensitive data such as internal network configurations, user credentials, or system identifiers. The vulnerability's exploitability is particularly dangerous because it requires no authentication and can be triggered remotely, making it an attractive target for automated exploitation campaigns. From an attack technique perspective, this vulnerability aligns with ATT&CK tactic TA0011: Command and Control, specifically technique T1071.004: Application Layer Protocol: DNS, as the information disclosure can occur through normal network protocols that appear legitimate to network monitoring systems. The outbound connection behavior creates a covert channel that can be used to exfiltrate data from compromised systems.
Mitigation strategies for CVE-2019-5152 primarily focus on immediate software updates and configuration hardening measures. Organizations should prioritize upgrading to shadowsocks-libev versions that contain the patched implementation, as the vulnerability was addressed in subsequent releases through improved packet validation and stream cipher handling. Network administrators should implement strict packet filtering rules that monitor and restrict unusual outbound connection patterns that may indicate exploitation attempts. The security community recommends deploying network segmentation strategies to limit the potential impact of successful exploitation, while also implementing comprehensive monitoring for anomalous outbound traffic that could indicate information disclosure activities. Additionally, organizations should conduct thorough security assessments of their shadowsocks implementations to identify other potential vulnerabilities in the network infrastructure that may compound the risks associated with this information disclosure flaw.