CVE-2026-51861 in Bisheng
Summary
by MITRE • 09/30/2026
bisheng 2.3.0, 2.4.0, and 2.4.0-beta1 is vulnerable to Code Injection in src/backend/bisheng/api/v1/validate.py.
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified in Bisheng versions 2.3.0 through 2.4.0-beta1 represents a critical server-side code injection flaw located within the validation module of the application's API layer. Specifically, the defect resides in the file src/backend/bisheng/api/v1/validate.py, where user-supplied input is processed without adequate sanitization or safe execution constraints before being evaluated by the Python interpreter. This architectural oversight allows an attacker to inject arbitrary malicious code snippets that are subsequently executed within the context of the running application process. The presence of this flaw indicates a fundamental failure in implementing secure coding practices regarding dynamic evaluation functions, such as eval() or exec(), which should never be used with untrusted input data under any circumstances.
From a technical perspective, the root cause is classified under CWE-94 Improper Control of Generation of Code (Code Injection). The vulnerability arises because the application accepts parameters that are directly passed to an execution engine without verifying their integrity or restricting them to a predefined set of safe operations. When the validation endpoint processes these inputs, it fails to distinguish between legitimate configuration data and executable payloads. This lack of input validation enables remote attackers to craft specific HTTP requests containing malicious Python code fragments. Upon receipt, the backend interprets this code as part of its internal logic, leading to arbitrary command execution on the host system where Bisheng is deployed.
The operational impact of this vulnerability is severe, potentially resulting in a complete compromise of the underlying infrastructure. An authenticated or unauthenticated attacker, depending on the specific access controls applied to the validation endpoint, can achieve remote code execution with the privileges assigned to the Bisheng service account. This capability allows for the exfiltration of sensitive data stored within the application's database, modification of system configurations, installation of persistent backdoors such as web shells or cryptominers, and lateral movement across the internal network if the compromised server has access to other critical assets. The severity is further amplified by the fact that code injection vulnerabilities are often trivially exploitable using automated tools, increasing the likelihood of successful attacks in the wild.
This vulnerability aligns with MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically sub-technique T1059.004 Python, as it involves the abuse of a scripting language to execute unauthorized commands. Additionally, it relates to CWE-78 Improper Neutralization of Special Elements used in an OS Command (OS Command Injection) if the injected code leads to shell command execution via os.system or similar functions. The exploitation path typically follows the pattern of initial access through the vulnerable API endpoint followed by privilege escalation and persistence mechanisms established through the executed payload.
To mitigate this risk, immediate remediation is required by upgrading Bisheng to a version that addresses this flaw, assuming an official patch has been released for versions 2.3.0 and above. In environments where updating is not immediately feasible, network-level controls should be implemented to restrict access to the /api/v1/validate endpoint only from trusted IP ranges or internal networks if public exposure is unnecessary. Input validation must also be enforced at a reverse proxy level using Web Application Firewall rules that detect patterns associated with Python code injection, such as common function calls like eval, exec, _import_, and os.system within query parameters or request bodies. Furthermore, developers should refactor the vulnerable code to eliminate dynamic evaluation entirely, replacing it with static configuration parsing libraries that do not interpret input as executable code. Regular security audits and static application security testing are recommended to prevent similar issues in future development cycles.