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medium·Product Based Web Vulnerabilities·Updated Jun 22, 2026

CVE-2026-54236 Scanner

CVE-2026-54236 Scanner - Information Disclosure vulnerability in vLLM

Est. Time~10 seconds
Scan TypeSingle Scan
Targetsdomain, subdomain, ipv4
CostFree
2k
Times Used
continuous scan runs
4.7k
Continuously Checked
assets under CS
0
Vulnerabilities Found
confirmed findings
References
CVECVE-2026-54236
5.3
CVSSmedium
Exploitable remotely over the internet · no authentication required.

vLLM is an inference and serving engine for large language models (LLMs). Prior to 0.23.1rc0, the fix for CVE-2026-22778, which introduced a sanitize_message helper that strips object-repr memory addresses from error messages before they reach the client, is incomplete: several response paths echo str(exc) directly to clients without calling sanitize_message. The unsanitized sites include the Anthropic API router in vllm/entrypoints/anthropic/api_router.py (the POST /v1/messages and POST /v1/messages/count_tokens handlers), the Server-Sent Events streaming converter in vllm/entrypoints/anthropic/serving.py, and the realtime speech-to-text WebSocket in vllm/entrypoints/speech_to_text/realtime/connection.py. These paths catch the exception inside the route coroutine and construct the JSONResponse themselves, bypassing the sanitizing global FastAPI exception handler, and WebSocket frames do not traverse that handler chain at all. Using the same primitive as the parent issue, an unauthenticated attacker can send malformed image bytes through the Anthropic Messages API image content parts so that PIL.Image.open raises an UnidentifiedImageError whose message contains the BytesIO object repr, leaking the heap memory address verbatim in the error.message field of the response body. This vulnerability is fixed in 0.23.1rc0.

Attack Vector
Network
Privileges Req.
None
User Interaction
None
Affected
vllmby vllm-project
< 0.23.1rc0
Updated Aug 22, 2026View on NVD →
Detail

vLLM is a product often utilized by artificial intelligence and machine learning developers to efficiently handle large language models. It is employed by organizations seeking scalable solutions for AI-powered applications, offering capabilities that manage computations and storage across distributed systems. The product's flexibility and handling of complex workflows make it a popular choice for research institutions, technology companies, and startups. Users deploy vLLM to align with dynamic AI tasks and initiatives, relying on its architecture to support varying model sizes and operational demands. Major enterprises value vLLM for its adaptability and performance in managing extensive AI data processes.

The vulnerability detected allows remote attackers to potentially leak heap addresses from the product, which can greatly diminish the effectiveness of Address Space Layout Randomization (ASLR). This flaw presents an opportunity for attackers to calculate system memory allocations more accurately, thus posing a risk of further exploits, such as remote code execution. Information disclosure vulnerabilities like this escalate risks by providing adversaries information to craft precise attacks. The problem arises from the Anthropic-compatible router improperly handling errors, specifically within the "/v1/messages" endpoint. Patch oversights are responsible for this continued vulnerability exploitation path in vLLM.

Technically, the vulnerability exists due to how errors are echoed back through the Anthropic-compatible router. Specifically, echoing str(exc) directly in the endpoint "/v1/messages" allows an attacker to infer heap addresses. The issue is exacerbated when the response includes internal error details, such as "_io.BytesIO object at 0x," coupled with status codes indicating a failure. These revelations occur despite attempts to sanitize responses, pointing to an incomplete fix in handling exceptions securely. The problem stems from insufficient validation and sanitization of error messages before they are returned in lightweight API structures.

If malicious actors exploit this vulnerability, they could achieve information disclosure that informs them of memory layout details. Such leaks can lead to precision attacks aiming at remote code execution or privilege escalation within affected systems. The ability to bypass security layers like ASLR provides adversaries with the groundwork for more sophisticated exploits, increasing the risk profile of the exposed service. Over time, consistent exposure to such vulnerabilities may undermine the reliability and security assurances the product seeks to provide its users.

REFERENCES

Solution Advice
  • Upgrade vLLM to a version newer than 0.23.0 to ensure patches for this vulnerability are applied.
  • Implement runtime security measures to monitor and alert unusual ASLR bypass attempts.
  • Restrict external access to the vulnerable endpoints with network security policies.
  • Regularly audit similar systems for misconfigurations that might reveal memory details.

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