Compliance Impact

The vulnerability allows an attacker to make the server issue arbitrary HTTP/HTTPS requests to internal services, potentially exposing internal resources. This could lead to unauthorized access to sensitive internal data or systems.

Such unauthorized access risks could impact compliance with standards and regulations like GDPR or HIPAA, which require protection of sensitive data and internal systems from unauthorized access or disclosure.

However, the CVE description and resources do not explicitly mention compliance impacts or specific regulatory considerations.

Useful 0 Not Useful 0

Executive Summary

CVE-2026-34753 is a Server-Side Request Forgery (SSRF) vulnerability in the vLLM project's batch runner, specifically in the function download_bytes_from_url.

This function downloads data from URLs specified in batch input JSON files, but it does so without validating or restricting the URLs. An attacker who can control the batch input JSON can make the server issue arbitrary HTTP or HTTPS requests to any URL.

Because there is no validation on the URL's hostname, IP address, port, path, query parameters, or redirects, the attacker can target internal services accessible from the vLLM host, such as cloud metadata endpoints or internal HTTP APIs.

This vulnerability exists in versions 0.16.0 up to before 0.19.0 and was fixed in version 0.19.0 by adding URL validation and domain allowlists.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability allows an attacker to make the vLLM server send arbitrary HTTP/HTTPS requests to internal or external services without authorization.

Potential impacts include unauthorized access to internal resources such as cloud metadata services or internal APIs, which could lead to information disclosure.

The CVSS score rates this vulnerability as moderate severity with a base score of 5.4, indicating a low complexity attack that requires low privileges and no user interaction.

The confidentiality impact is low, integrity impact is none, and availability impact is low.

Useful 0 Not Useful 0

Detection Guidance

This vulnerability can be detected by monitoring for unusual or unexpected HTTP/HTTPS requests originating from the vLLM server, especially those triggered by batch input JSON files containing the `file_url` field.

Since the vulnerability involves the server making arbitrary HTTP requests without validation, detection can focus on identifying such requests to internal or unexpected external endpoints.

• Use network monitoring tools (e.g., tcpdump, Wireshark) to capture outgoing HTTP/HTTPS traffic from the vLLM host.
• Run commands like `tcpdump -i <interface> tcp port 80 or tcp port 443` to capture HTTP/HTTPS traffic.
• Inspect logs of the vLLM batch runner for batch input JSON files containing suspicious or unexpected URLs in the `file_url` field.
• Use application-level logging or debugging to trace calls to the `download_bytes_from_url` function and verify the URLs being requested.

Useful 0 Not Useful 0

Mitigation Strategies

The immediate and recommended mitigation is to upgrade the vLLM package to version 0.19.0 or later, where the vulnerability is fixed by implementing URL validation and domain allowlists.

If upgrading is not immediately possible, restrict access to the vLLM batch runner to trusted users only, and carefully validate or sanitize batch input JSON files to prevent attacker-controlled URLs.

Additionally, network-level controls such as firewall rules can be applied to restrict the vLLM server's outbound HTTP/HTTPS requests to only trusted domains or IP ranges.

Useful 0 Not Useful 0