CVE-2023-54403 in U8 CRM
Summary
by MITRE • 10/01/2026
Yonyou U8 CRM before V16.5 and V18 contains an arbitrary file read vulnerability in /ajax/getemaildata.php that allows unauthenticated attackers to bypass authentication using the DontCheckLogin=1 parameter and read arbitrary files via an unvalidated filePath parameter. Attackers can exploit this flaw to read sensitive files outside the web application directory, including configuration files containing database or service credentials. Exploitation evidence was first observed by the Shadowserver Foundation on 2023-10-14.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified in Yonyou U8 CRM versions prior to V16.5 and V18 represents a critical security flaw classified as an arbitrary file read issue, specifically located within the /ajax/getemaildata.php endpoint. This weakness stems from insufficient input validation regarding the filePath parameter passed by the client application. In secure software design, any user-supplied path used for file operations must be strictly validated against a whitelist of allowed directories or sanitized to prevent directory traversal sequences such as ../ from escaping the intended context. The absence of these safeguards allows an unauthenticated attacker to manipulate this parameter and access files residing anywhere on the server's filesystem that are readable by the web application process user. This is not merely a local information disclosure but a mechanism for remote data exfiltration with no prior authentication required, significantly lowering the barrier to entry for malicious actors seeking sensitive system intelligence.
The operational impact of this vulnerability is severe due to its unauthenticated nature and the potential scope of accessible data. By leveraging the DontCheckLogin=1 parameter, attackers can bypass standard authentication mechanisms entirely, treating the endpoint as a public interface rather than a protected resource. Once authenticated access is circumvented, the attacker can read arbitrary files outside the web application directory structure. This capability enables the extraction of configuration files that often contain plaintext database credentials, service account passwords, and other sensitive connection strings. Compromise of these credentials typically leads to further lateral movement within the network, allowing attackers to pivot from file reading to direct database access or remote code execution depending on the privileges associated with those extracted accounts. The ability to read system-level configuration files effectively neutralizes many traditional perimeter defenses since the attacker gains deep insight into the internal architecture and security posture of the target environment.
Evidence of active exploitation for this vulnerability was first observed by the Shadowserver Foundation on October 14, 2023, indicating that threat actors are actively scanning for and exploiting this flaw in the wild. This real-world activity underscores the urgency of remediation, as unpatched systems remain vulnerable to automated attacks from botnets and opportunistic hackers alike. The presence of such exploitation evidence suggests that organizations running affected versions should be considered compromised or at high risk until patches are applied. Security teams must prioritize this vulnerability in their patch management cycles due to its ease of exploitation and the critical nature of the data it exposes.
From a technical classification perspective, this flaw aligns with CWE-22: Improper Limitation of a Pathname to a Restricted Directory, which describes vulnerabilities where software does not properly neutralize special elements within file paths that can cause files to be located outside of the intended directory. Additionally, the exploitation technique maps directly to MITRE ATT&CK techniques related to Discovery and Collection, specifically T1083: File and Directory Discovery and potentially T1504: Weak or Reused Credentials if the extracted configuration files are used for further access. The bypass of authentication via DontCheckLogin=1 also relates to CWE-287: Improper Authentication, highlighting a failure in enforcing identity verification before granting resource access.
Mitigation strategies must focus on immediate patching and compensating controls until updates are deployed. Organizations should upgrade Yonyou U8 CRM to version V16.5 or later where the input validation for filePath has been corrected. In environments where immediate patching is not feasible, network-level mitigations such as Web Application Firewall rules can be configured to block requests containing directory traversal patterns in file path parameters and to restrict access to the /ajax/getemaildata.php endpoint based on IP reputation or authentication status. Furthermore, administrators should audit server permissions to ensure that the web application process runs with minimal privileges, limiting the impact of any successful file read attempts by restricting which system files are accessible to the service account running the application. Regular monitoring for signs of exploitation, such as unusual outbound traffic patterns associated with data exfiltration or access logs showing repeated failed authentication followed by successful unauthenticated requests, is also recommended to detect potential compromises early.