{"id":"CVE-2026-73555","aliases":["EUVD-2026-58053","GHSA-hwrm-c4cx-rf4j","PYSEC-2026-3937"],"status":"published","title":"vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages","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.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00413,"percentile":0.35974,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-209"],"published":"2026-08-13T14:50:03Z","modified":"2026-11-04T02:45:46Z","fixes":[{"ecosystem":"PyPI","package":"vllm","fixed_in":["0.26.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"vllm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.26.0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"vllm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.26.0"}]}],"versions":["0.0.1","0.1.0","0.1.1","0.1.2","0.1.3","0.1.4","0.1.5","0.1.6","0.1.7","0.10.0","0.10.1","0.10.1.1","0.10.2","0.11.0","0.11.1","0.11.2","0.12.0","0.13.0","0.14.0","0.14.1","0.15.0","0.15.1","0.16.0","0.17.0","0.17.1","0.18.0","0.18.1","0.19.0","0.19.1","0.2.0","0.2.1","0.2.1.post1","0.2.2","0.2.3","0.2.4","0.2.5","0.2.6","0.2.7","0.20.0","0.20.1","0.20.2","0.21.0","0.22.0","0.22.1","0.23.0","0.24.0","0.25.0","0.25.1","0.3.0","0.3.1","0.3.2","0.3.3","0.4.0","0.4.0.post1","0.4.1","0.4.2","0.4.3","0.5.0","0.5.0.post1","0.5.1","0.5.2","0.5.3","0.5.3.post1","0.5.4","0.5.5","0.6.0","0.6.1","0.6.1.post1","0.6.1.post2","0.6.2","0.6.3","0.6.3.post1","0.6.4","0.6.4.post1","0.6.5","0.6.6","0.6.6.post1","0.7.0","0.7.1","0.7.2","0.7.3","0.8.0","0.8.1","0.8.2","0.8.3","0.8.4","0.8.5","0.8.5.post1","0.9.0","0.9.0.1","0.9.1","0.9.2"]},{"source":"osv","ecosystem":"PyPI","package":"vllm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.26.0"}]}],"versions":["0.0.1","0.1.0","0.1.1","0.1.2","0.1.3","0.1.4","0.1.5","0.1.6","0.1.7","0.10.0","0.10.1","0.10.1.1","0.10.2","0.11.0","0.11.1","0.11.2","0.12.0","0.13.0","0.14.0","0.14.1","0.15.0","0.15.1","0.16.0","0.17.0","0.17.1","0.18.0","0.18.1","0.19.0","0.19.1","0.2.0","0.2.1","0.2.1.post1","0.2.2","0.2.3","0.2.4","0.2.5","0.2.6","0.2.7","0.20.0","0.20.1","0.20.2","0.21.0","0.22.0","0.22.1","0.23.0","0.24.0","0.25.0","0.25.1","0.3.0","0.3.1","0.3.2","0.3.3","0.4.0","0.4.0.post1","0.4.1","0.4.2","0.4.3","0.5.0","0.5.0.post1","0.5.1","0.5.2","0.5.3","0.5.3.post1","0.5.4","0.5.5","0.6.0","0.6.1","0.6.1.post1","0.6.1.post2","0.6.2","0.6.3","0.6.3.post1","0.6.4","0.6.4.post1","0.6.5","0.6.6","0.6.6.post1","0.7.0","0.7.1","0.7.2","0.7.3","0.8.0","0.8.1","0.8.2","0.8.3","0.8.4","0.8.5","0.8.5.post1","0.9.0","0.9.0.1","0.9.1","0.9.2"]}],"products":[{"vendor":"vllm","product":"vllm"},{"vendor":"vllm-project","product":"vllm"}],"references":[{"url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-hwrm-c4cx-rf4j","tags":["x_refsource_CONFIRM","Mitigation","Vendor Advisory","advisory","web"]},{"url":"https://github.com/vllm-project/vllm/pull/46415","tags":["x_refsource_MISC","Issue Tracking","Patch","fix","web"]},{"url":"https://github.com/vllm-project/vllm/commit/e87521626febe2763f997691d1599de4175f4324","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/vllm-project/vllm/releases/tag/v0.26.0","tags":["x_refsource_MISC","Release Notes","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73555","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-hwrm-c4cx-rf4j","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73555.json","tags":["advisory"]},{"url":"https://github.com/vllm-project/vllm","tags":["package"]},{"url":"https://pypi.org/project/vllm","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-73555","title":"vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages","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.","status":"published","published":"2026-08-13T14:50:03.539Z","modified":"2026-08-14T15:57:23.396Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-209"],"updated_at":"2026-11-02T13:43:33.766176Z"}],"euvd":[{"id":"EUVD-2026-58053","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.","status":"published","published":"2026-08-13T14:50:03Z","modified":"2026-08-14T15:57:23Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T18:01:54.910263Z"}],"ghsa":[{"id":"GHSA-hwrm-c4cx-rf4j","title":"vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages","description":"## Summary\n\nWhen the vLLM API receives a malformed request (e.g., invalid JSON or missing required fields), FastAPI raises a Pydantic `RequestValidationError`. The `validation_exception_handler` in `vllm/entrypoints/openai/server_utils.py` converts this exception to a string via `str(exc)`, which includes the internal file path and line number of the handler function. The existing `sanitize_message()` function in `vllm/entrypoints/utils.py` strips memory addresses (e.g., `0x7f...`) but does not strip `File \"...\", line X` patterns. The result is a user-facing HTTP response that leaks internal system information.\n\n## Impact\n\nAn unauthenticated attacker can extract the following with a single malformed request:\n\n- **OS username** running the vLLM process (e.g., `ubuntu`)\n- **Home directory path** (e.g., `/home/ubuntu/`)\n- **Virtual environment path** (e.g., `vllm-env/`)\n- **Python version** (e.g., `3.12`)\n- **Internal package structure and line numbers** (e.g., `vllm/entrypoints/openai/chat_completion/api_router.py`)\n- **Handler function names per endpoint**, enabling precise version fingerprinting\n\nThis information aids attackers in constructing targeted exploits: environment paths narrow the attack surface, and handler function names + line numbers enable exact version identification even when the `/version` endpoint is disabled.\n\nAll POST endpoints that accept JSON bodies are affected, including `/v1/chat/completions`, `/v1/completions`, `/tokenize`, and `/detokenize`.\n\n## Workarounds\n\nDeploying vLLM behind a reverse proxy that rewrites error response bodies to strip file paths would mitigate this, though it is fragile.\n\n## Remediation Recommendation\n\nTwo possible fixes (either suffices):\n\n**Option A — Fix `validation_exception_handler`:** Construct the error message from `exc.errors()` (the structured Pydantic error list) rather than `str(exc)`. This avoids the traceback-style string entirely.\n\n**Option B — Fix `sanitize_message`:** Add a regex to strip `File \"...\", line \\d+` patterns, similar to how memory addresses are already stripped:\n\n```python\nimport re\nmsg = re.sub(r'File \".*?\", line \\d+, in \\w+', '[internal]', msg)\n```\n\nOption A is preferred as it addresses the root cause rather than filtering symptoms.\n\n## Environment Tested\n\n- vLLM 0.20.1 (pip install, latest stable as of May 2026)\n- Python 3.12\n- Ubuntu 22.04\n- Model: Qwen/Qwen2-0.5B (text-only; bug is model-independent)\n\nThis was fixed here: https://github.com/vllm-project/vllm/commit/e87521626f","status":"published","published":"2026-09-04T21:36:33Z","modified":"2026-09-04T21:36:35Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"cwes":["CWE-209"],"updated_at":"2026-11-02T14:41:13.477974Z"}],"nvd":[{"id":"CVE-2026-73555","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.","status":"published","published":"2026-08-13T15:20:17.773Z","modified":"2026-10-02T19:28:34.51Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-209"],"updated_at":"2026-11-02T14:12:37.557758Z"}],"osv":[{"id":"CVE-2026-73555","title":"vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages","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.","status":"published","published":"2026-08-13T14:50:03.539Z","modified":"2026-11-10T02:32:39.34988211Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"cwes":["CWE-209"],"updated_at":"2026-11-10T02:45:42.584685Z"},{"id":"GHSA-hwrm-c4cx-rf4j","title":"vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages","description":"## Summary\n\nWhen the vLLM API receives a malformed request (e.g., invalid JSON or missing required fields), FastAPI raises a Pydantic `RequestValidationError`. The `validation_exception_handler` in `vllm/entrypoints/openai/server_utils.py` converts this exception to a string via `str(exc)`, which includes the internal file path and line number of the handler function. The existing `sanitize_message()` function in `vllm/entrypoints/utils.py` strips memory addresses (e.g., `0x7f...`) but does not strip `File \"...\", line X` patterns. The result is a user-facing HTTP response that leaks internal system information.\n\n## Impact\n\nAn unauthenticated attacker can extract the following with a single malformed request:\n\n- **OS username** running the vLLM process (e.g., `ubuntu`)\n- **Home directory path** (e.g., `/home/ubuntu/`)\n- **Virtual environment path** (e.g., `vllm-env/`)\n- **Python version** (e.g., `3.12`)\n- **Internal package structure and line numbers** (e.g., `vllm/entrypoints/openai/chat_completion/api_router.py`)\n- **Handler function names per endpoint**, enabling precise version fingerprinting\n\nThis information aids attackers in constructing targeted exploits: environment paths narrow the attack surface, and handler function names + line numbers enable exact version identification even when the `/version` endpoint is disabled.\n\nAll POST endpoints that accept JSON bodies are affected, including `/v1/chat/completions`, `/v1/completions`, `/tokenize`, and `/detokenize`.\n\n## Workarounds\n\nDeploying vLLM behind a reverse proxy that rewrites error response bodies to strip file paths would mitigate this, though it is fragile.\n\n## Remediation Recommendation\n\nTwo possible fixes (either suffices):\n\n**Option A — Fix `validation_exception_handler`:** Construct the error message from `exc.errors()` (the structured Pydantic error list) rather than `str(exc)`. This avoids the traceback-style string entirely.\n\n**Option B — Fix `sanitize_message`:** Add a regex to strip `File \"...\", line \\d+` patterns, similar to how memory addresses are already stripped:\n\n```python\nimport re\nmsg = re.sub(r'File \".*?\", line \\d+, in \\w+', '[internal]', msg)\n```\n\nOption A is preferred as it addresses the root cause rather than filtering symptoms.\n\n## Environment Tested\n\n- vLLM 0.20.1 (pip install, latest stable as of May 2026)\n- Python 3.12\n- Ubuntu 22.04\n- Model: Qwen/Qwen2-0.5B (text-only; bug is model-independent)\n\nThis was fixed here: https://github.com/vllm-project/vllm/commit/e87521626f","status":"published","published":"2026-09-04T21:36:33Z","modified":"2026-09-10T12:25:54.771951503Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"cwes":["CWE-209"],"updated_at":"2026-11-02T15:46:49.621585Z"},{"id":"PYSEC-2026-3937","title":"vLLM: Unauthenticated Internal Path and Username Disclosure via Validation Error Messages","description":"## Summary\n\nWhen the vLLM API receives a malformed request (e.g., invalid JSON or missing required fields), FastAPI raises a Pydantic `RequestValidationError`. The `validation_exception_handler` in `vllm/entrypoints/openai/server_utils.py` converts this exception to a string via `str(exc)`, which includes the internal file path and line number of the handler function. The existing `sanitize_message()` function in `vllm/entrypoints/utils.py` strips memory addresses (e.g., `0x7f...`) but does not strip `File \"...\", line X` patterns. The result is a user-facing HTTP response that leaks internal system information.\n\n## Impact\n\nAn unauthenticated attacker can extract the following with a single malformed request:\n\n- **OS username** running the vLLM process (e.g., `ubuntu`)\n- **Home directory path** (e.g., `/home/ubuntu/`)\n- **Virtual environment path** (e.g., `vllm-env/`)\n- **Python version** (e.g., `3.12`)\n- **Internal package structure and line numbers** (e.g., `vllm/entrypoints/openai/chat_completion/api_router.py`)\n- **Handler function names per endpoint**, enabling precise version fingerprinting\n\nThis information aids attackers in constructing targeted exploits: environment paths narrow the attack surface, and handler function names + line numbers enable exact version identification even when the `/version` endpoint is disabled.\n\nAll POST endpoints that accept JSON bodies are affected, including `/v1/chat/completions`, `/v1/completions`, `/tokenize`, and `/detokenize`.\n\n## Workarounds\n\nDeploying vLLM behind a reverse proxy that rewrites error response bodies to strip file paths would mitigate this, though it is fragile.\n\n## Remediation Recommendation\n\nTwo possible fixes (either suffices):\n\n**Option A — Fix `validation_exception_handler`:** Construct the error message from `exc.errors()` (the structured Pydantic error list) rather than `str(exc)`. This avoids the traceback-style string entirely.\n\n**Option B — Fix `sanitize_message`:** Add a regex to strip `File \"...\", line \\d+` patterns, similar to how memory addresses are already stripped:\n\n```python\nimport re\nmsg = re.sub(r'File \".*?\", line \\d+, in \\w+', '[internal]', msg)\n```\n\nOption A is preferred as it addresses the root cause rather than filtering symptoms.\n\n## Environment Tested\n\n- vLLM 0.20.1 (pip install, latest stable as of May 2026)\n- Python 3.12\n- Ubuntu 22.04\n- Model: Qwen/Qwen2-0.5B (text-only; bug is model-independent)\n\nThis was fixed here: https://github.com/vllm-project/vllm/commit/e87521626f","status":"published","published":"2026-09-10T09:45:00.131177Z","modified":"2026-09-10T12:15:14.071548189Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T15:52:57.255153Z"}]}}