CVE-2026-54236

Name of the Vulnerable Software and Affected Versions vLLM versions prior to 0.23.1rc0

Description An incomplete fix for a previous memory leak issue allows unauthenticated attackers to leak heap memory addresses. The system fails to properly sanitize error messages in several response paths, echoing the string representation of exceptions directly to clients. This occurs because certain routes catch exceptions internally and construct responses themselves, bypassing the global sanitizing exception handler, while WebSocket frames bypass the handler chain entirely.

Technical details include:

An attacker can exploit this by sending malformed image bytes through the Anthropic Messages API image content parts. This causes the PIL.Image.open() function to raise an UnidentifiedImageError, which includes a BytesIO object representation containing a verbatim heap memory address in the error.message field of the response body.

Recommendations Update to version 0.23.1rc0 or later. As a temporary workaround, restrict access to the 'POST /v1/messages' and 'POST /v1/messages/count tokens' endpoints and the realtime speech-to-text WebSocket to minimize the risk of exploitation.