Submit #1004351: SGLang Project (sgl-project) SGLang(SGLang Runtime) 0.5.19 Improper Validation of Specified Type of Input

SGLang 0.5.19 contains a denial-of-service vulnerability in the handling of session parameters submitted to its native generation API. The request model accepts session_params as a dictionary containing arbitrary values, and the tokenizer manager constructs a SessionParams object without enforcing its annotated field types at runtime.

Consequently, incorrectly typed values can pass through the request-processing boundary and reach scheduler-side session management, where operations that assume valid types raise a TypeError. The proposed fix adds explicit runtime validation and converts validation failures into request-level errors.

The reported failure is not confined to the malformed request. The scheduler exception triggers SIGQUIT-driven shutdown of the serving instance, interrupting in-flight requests and leaving the health endpoint unreachable. A remote client with access to the affected generation API can therefore cause service-wide denial of service. The session-identifier failure does not require a pre-existing session. Authentication requirements depend on the access controls protecting the deployed API; the report does not establish an authentication bypass.

Proposed fix:
https://github.com/sgl-project/sglang/pull/41535

• Source: ⚠️ https://github.com/sgl-project/sglang/issues/41467
• User: Zyz3366 (UID 97230)
• Submission: 09/28/2026 20:42 (27 days ago)
• Moderation: 10/14/2026 20:11 (16 days later)
• Status: Accepted
• VulDB entry: 420278 [sgl-project SGLang up to 0.5.19 generate Endpoint io_struct.py session_params denial of service]
• Points: 20