CVE-2026-109423 in Cloud Music
Summary
by MITRE • 10/12/2026
NetEase Cloud Music client for Windows (cloudmusic.exe) versions 3.1.38 and 3.1.39.205426 contains a TLS certificate validation vulnerability that allows a network-adjacent attacker to intercept and decrypt HTTPS traffic by failing to validate the server certificate chain, verify the hostname, or consult any Windows certificate trust store. Attackers can perform a man-in-the-middle attack using a rogue certificate authority to decrypt traffic, capture the MUSIC_U session credential sent in authenticated API requests, and modify server responses in transit, enabling account takeover and transport-layer response forgery.
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Analysis
by VulDB Data Team • 10/12/2026
The vulnerability identified in NetEase Cloud Music client for Windows versions 3.1.38 and 3.1.39.205426 represents a critical failure in the implementation of Transport Layer Security (TLS) protocols within the application's networking stack. The core technical flaw lies in the complete bypassing of standard certificate validation procedures during HTTPS connections. Specifically, the client fails to validate the server certificate chain against trusted root authorities, neglects to verify that the hostname presented by the server matches the expected domain name, and entirely ignores the Windows system certificate trust store which typically contains verified public key infrastructure certificates. This misconfiguration effectively disables mutual authentication mechanisms at the transport layer, allowing any network-adjacent attacker to intercept communications without triggering security warnings or connection failures in the client application.
From an operational perspective, this vulnerability enables sophisticated man-in-the-middle attacks where an adversary can position themselves between the user and the NetEase Cloud Music servers. By utilizing a rogue certificate authority that has been installed on the victim's machine through social engineering, malware, or other compromise methods, attackers can generate valid-looking certificates for any domain associated with the service. Since the client does not validate these certificates against known trust anchors, it accepts them as legitimate. This allows the attacker to decrypt all HTTPS traffic transparently, gaining full visibility into sensitive data transmitted between the application and the server. The most significant consequence of this decryption capability is the exposure of the MUSIC_U session credential, which serves as a primary authentication token for API requests made by the client.
The interception of the MUSIC_U credential poses severe security implications, primarily facilitating account takeover attacks. Once an attacker captures this session token, they can replay it to authenticate as the victim user without needing their password or multi-factor authentication credentials. This effectively grants the attacker full control over the compromised account, including access to personal playlists, listening history, and potentially linked payment information if such features are integrated into the API endpoints accessed via these authenticated requests. Furthermore, because the client does not verify server identity, attackers can also modify server responses in transit. This capability enables transport-layer response forgery, where malicious content or commands embedded in modified HTTP responses could be executed by the application logic, potentially leading to further exploitation vectors such as cross-site scripting if the data is rendered improperly within the desktop environment's web views or other UI components.
This vulnerability aligns with Common Weakness Enumeration (CWE) identifiers including CWE-295 Improper Certificate Validation and CWE-319 Cleartext Transmission of Sensitive Information. In terms of the MITRE ATT&CK framework, this flaw facilitates techniques categorized under Credential Access via Network Sniffing as well as Defense Evasion through Obfuscated Files or Information if combined with other evasion tactics to hide the malicious certificate installation. The lack of hostname verification specifically relates to CWE-296 which covers Improper Following of a Certificate's Chain of Trust. These weaknesses collectively undermine the fundamental security guarantees provided by TLS, reducing encrypted channels to mere obfuscation layers that offer no protection against determined adversaries with network access and basic cryptographic capabilities.
Mitigation strategies must prioritize immediate software updates to versions where certificate validation is correctly implemented according to industry standards such as RFC 5280 for X.509 Certificate Validation. Users should ensure their NetEase Cloud Music client is updated to the latest stable release which addresses these TLS implementation flaws. In environments where automatic updating may be delayed, network-level controls can provide temporary relief by deploying deep packet inspection solutions that validate certificates independently of the application's behavior or by restricting outbound HTTPS traffic to only known and verified endpoints through strict firewall rules. Additionally, organizations should enforce policies that prevent unauthorized certificate authorities from being installed in the Windows system trust store, as this is often a prerequisite for successfully exploiting this specific vulnerability using rogue CA attacks. Regular security audits focusing on cryptographic implementation details within third-party desktop applications are essential to identify similar misconfigurations before they can be exploited at scale.