CVE-2026-59152 in LangSmith SDK
Summary
by MITRE • 07/06/2026
LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. Prior to 0.8.18, an attacker who can send an HTTP request to a server running the LangSmith SDK's TracingMiddleware can cause that server to read an arbitrary file from its local filesystem and upload the contents to LangSmith as a trace attachment. Depending on how the distributed trace system is deployed, triggering a read may not require authentication. Retrieving the contents requires read access to the LangSmith workspace the traces are sent to. The net effect is a trust-boundary crossing: a party with workspace trace-read access (for example a low-privilege workspace member, a contractor, or a compromised teammate account) gains the ability to read files from any server running TracingMiddleware, a capability outside that workspace's intended trust boundary. This vulnerability is fixed in 0.8.18.
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Analysis
by VulDB Data Team • 07/06/2026
The LangSmith Client SDKs represent a distributed tracing solution that enables developers to instrument applications and collect telemetry data for observability purposes. The TracingMiddleware component serves as a critical integration point within applications, capturing execution traces and transmitting them to the LangSmith platform for analysis and monitoring. This middleware functionality creates a trust boundary where the application's internal operations are exposed to external systems through trace collection mechanisms.
The vulnerability stems from insufficient input validation within the TracingMiddleware implementation that processes HTTP requests containing trace data. When an attacker crafts a malicious HTTP request with specially formatted parameters, the middleware fails to properly sanitize file path references, allowing arbitrary file system traversal and reading operations. This flaw exists in versions prior to 0.8.18 where proper security controls were not implemented to validate or restrict file system access during trace processing.
The operational impact of this vulnerability extends beyond typical file system access issues as it represents a significant trust boundary violation within distributed tracing systems. An attacker with merely read access to a LangSmith workspace can exploit this vulnerability to extract sensitive information from servers running the affected SDK middleware. This includes configuration files, credentials, application source code, and other potentially sensitive data that may be accessible through standard file system paths. The attack does not require authentication to trigger the file reading functionality, making it particularly dangerous in environments where trace data collection is exposed to untrusted parties.
The security implications align with CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-73 (Restriction of Files with Improper Access Control), demonstrating how improper validation of user-supplied input can lead to unauthorized file system access. From an adversary perspective, this vulnerability maps to ATT&CK technique T1083 (File and Directory Discovery) and T1566 (Phishing for Information), as it provides a mechanism for attackers to discover and exfiltrate sensitive files through legitimate trace collection channels. The compromise of a single compromised account or low-privilege workspace member can potentially escalate to full system file access across all servers running the affected middleware.
The fix implemented in version 0.8.18 addresses this vulnerability by introducing proper input validation and sanitization for file paths within the TracingMiddleware component. This includes implementing strict path validation, restricting file system access to predefined safe directories, and ensuring that trace data processing does not permit arbitrary file reading operations. Organizations should immediately upgrade to version 0.8.18 or later to remediate this vulnerability and ensure proper isolation between workspace access controls and underlying file system access permissions.