LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. Prior to version 0.5.18, the LangSmith JavaScript/TypeScript SDK (langsmith) contains an incomplete prototype pollution fix in its internally vendored lodash set() utility. The baseAssignValue() function only guards against the __proto__ key but fails to prevent traversal via constructor.prototype. This allows an attacker who controls keys in data processed by the createAnonymizer() API to pollute Object.prototype, affecting all objects in the Node.js process. This vulnerability is fixed in version 0.5.18.
The CVSS score for this vulnerability is 5.6, classifying it as medium severity, indicating that it poses a significant risk to organizations. The attack vector is network-based with a high attack complexity, meaning that successful exploitation requires a sophisticated approach. Given the nature of the vulnerability, it does not require any privileges or user interaction to exploit.
Risk to organizations includes potential impacts on confidentiality, integrity, and availability, as attackers may leverage this vulnerability to affect the behavior of all objects within the Node.js process. Organizations should prioritize patching immediately.
As of now, there are no known exploits or public proof of concept code available for this vulnerability. However, the CVE status is marked as deferred, which indicates that further evaluation of its impact and remediation may be necessary.
To protect against this vulnerability, organizations should ensure that they update their LangSmith SDK to version 0.5.18 or later as soon as possible.
Vulnerability Details
The vulnerability allows for prototype pollution via incomplete guarding of the lodash set() utility within the LangSmith SDK. The CVSS 3.1 score indicates a medium severity level with a vector string of 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L', highlighting the network attack vector and high attack complexity.
The affected product is the LangSmith JavaScript/TypeScript SDK, specifically prior to version 0.5.18. The vulnerability was published on April 10, 2026, and is classified under CWE-1321.
Technical Analysis
The root cause of the vulnerability lies in the incomplete implementation of the prototype pollution fix in the lodash set() utility. Specifically, the function baseAssignValue() fails to guard against object traversal via constructor.prototype, allowing attackers to manipulate Object.prototype.
The attack vector is network-based, requiring no privileges or user interaction. The complexity is rated as high, meaning attackers would need to develop a sophisticated approach to exploit this vulnerability effectively.
Risk & Impact Analysis
Real-world deployment risk includes the potential for attackers to pollute Object.prototype, which could lead to unexpected behavior across all objects within the Node.js process. This could compromise the integrity of applications relying on the LangSmith SDK.
The blast radius potential is significant as the vulnerability affects all instances of the SDK in use, making it critical for organizations to address. Urgency assessment based on the CVSS score suggests that organizations should address this vulnerability in their priority patch cycle.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions prior to vendor patch version 0.5.18 are affected. Organizations are advised to apply the latest updates to ensure protection against this vulnerability.
Mitigation & Remediation
Organizations should prioritize patching the LangSmith SDK to version 0.5.18 or later. Regularly updating dependencies can help mitigate potential vulnerabilities. For continuous security, organizations may consider engaging in continuous penetration testing to identify and address similar weaknesses in their applications.
Detection Guidance
Organizations should monitor logs for any unexpected object behavior and track changes in object constructors that may indicate exploitation attempts. Additionally, behavioral anomalies in applications interacting with the LangSmith SDK should be closely observed.
AppSecure Threat Intelligence Insight
The long-term significance of this vulnerability lies in its potential to disrupt application integrity via prototype pollution. Security teams should recognize the trend of vulnerabilities related to object manipulation and ensure that proper defensive coding practices are in place.
In light of this vulnerability, organizations are encouraged to review their security posture and consider implementing comprehensive vulnerability management programs that prioritize the identification and mitigation of similar issues.
Furthermore, organizations should stay informed about emerging trends in software vulnerabilities and continuously enhance their security frameworks to adapt to evolving threats.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
.webp)