Uncontrolled Resource Consumption in vLLM: Understanding and Mitigating CVE-2026-116177

Overview

CVE-2026-116177 is an uncontrolled resource consumption vulnerability in the vLLM (very large language model) package, specifically affecting versions from 0.10.2 up to but not including 0.25.0. This vulnerability is particularly concerning because it allows unauthenticated attackers to cause a denial-of-service (DoS) by submitting a specially crafted image that can exhaust the memory of the system. The affected versions of vLLM use the Nemotron-VL processors, which globally set Image.MAX_IMAGE_PIXELS to None, making it possible for attackers to bypass security checks and trigger an Out-of-Memory (OOM) condition.

Understanding the Vulnerability / Threat

Root Cause Analysis

The root cause of this vulnerability is the global setting of Image.MAX_IMAGE_PIXELS to None in the Nemotron-VL processors used by vLLM. This setting allows for images of any size to be processed without restrictions, enabling an attacker to submit a 'decompression bomb'—a small image that expands to a much larger size when processed. This can lead to uncontrolled resource consumption, as the system attempts to handle an image that requires an excessive amount of memory. This vulnerability falls under the CWE-400 category, which covers 'Uncontrolled Resource Consumption' vulnerabilities.

Attack Surface & Vector

The attack surface for CVE-2026-116177 is the /v1/chat/completions endpoint of the vLLM service. An unauthenticated attacker can send a specially crafted HTTP request with a pathological decompression-bomb image. The attack vector is network-adjacent, with no prerequisites other than network access to the targeted service.

Exploitation Mechanics — Scenario Walkthrough

Scenario: Compromising a Corporate vLLM Instance 1. Initial Position: An attacker gains network access to a corporate server running a vulnerable version of vLLM (e.g., version 0.20.0). 2. Triggering the Flaw: The attacker crafts an HTTP POST request to the /v1/chat/completions endpoint with a specially designed image that acts as a decompression bomb. This image is designed to expand to a size that exceeds the available memory when processed. 3. What Breaks: When the vLLM service processes this image, it attempts to allocate an excessive amount of memory, leading to an Out-of-Memory (OOM) condition. This causes the worker process to crash, potentially denying service to other tenants or users of the system. 4. Attacker's Prize: The attacker successfully triggers a denial-of-service condition, impacting the availability of the vLLM service for legitimate users. This could lead to operational disruptions, especially in environments relying on vLLM for critical tasks.

Real-World Impact

The impact of CVE-2026-116177 can be significant, particularly in multi-tenant environments where a single tenant can cause resource exhaustion, affecting others. An attacker could exploit this vulnerability to disrupt service, causing financial loss, operational delays, or reputational damage. While there is no evidence of active exploitation in the wild, the severity of the vulnerability (CVSS score of 7.5) underscores the need for prompt mitigation.

Detection & Defense

Immediate Mitigations

- Upgrade vLLM to version 0.25.0 or later. - Implement rate limiting on the /v1/chat/completions endpoint to restrict the number of requests from a single IP address within a given time frame. - Configure Image.MAX_IMAGE_PIXELS to a reasonable limit if possible.

Detection Strategies

- Monitor for unusual patterns of requests to the /v1/chat/completions endpoint, especially those with large or suspiciously crafted images. - Implement SIEM rules to detect and alert on potential decompression bomb attacks. - Use network intrusion detection systems (NIDS) to identify and block malicious traffic.

Long-Term Hardening

- Regularly update and patch vLLM and its dependencies. - Implement robust security measures, such as authentication and rate limiting, for all API endpoints. - Conduct regular security audits and vulnerability assessments to identify and address potential weaknesses.

Key Takeaways

- CVE-2026-116177 is an uncontrolled resource consumption vulnerability in vLLM that can lead to denial-of-service attacks. - The vulnerability is caused by the global setting of Image.MAX_IMAGE_PIXELS to None in Nemotron-VL processors. - Immediate mitigation involves upgrading to vLLM version 0.25.0 or later and implementing rate limiting. - Detection strategies include monitoring API requests and implementing SIEM rules. - Long-term hardening involves regular updates, security audits, and robust API security measures.

Sources

- National Vulnerability Database (NVD) - CVE-2026-116177 - Vulncheck - Vulnerability Details for vLLM