Skip to main content

CVE-2026-34753

| EUVDEUVD-2026-19349 MEDIUM
Server-Side Request Forgery (SSRF) (CWE-918)
2026-04-03 https://github.com/vllm-project/vllm GHSA-pf3h-qjgv-vcpr
5.4
CVSS 3.1 · GitHub Advisory
Share

Severity by source

GitHub Advisory PRIMARY
5.4 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L
Red Hat
5.4 MEDIUM
qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
Low

Lifecycle Timeline

4
EUVD ID Assigned
Apr 03, 2026 - 22:15 euvd
EUVD-2026-19349
Analysis Generated
Apr 03, 2026 - 22:15 vuln.today
Patch released
Apr 03, 2026 - 22:15 nvd
Patch available
CVE Published
Apr 03, 2026 - 21:51 nvd
MEDIUM 5.4

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 4 pypi packages depend on vllm (4 direct, 0 indirect)

Ecosystem-wide dependent count for version 0.16.0.

DescriptionGitHub Advisory

Summary

A Server Side Request Forgery (SSRF) vulnerability in download_bytes_from_url allows any actor who can control batch input JSON to make the vLLM batch runner issue arbitrary HTTP/HTTPS requests from the server, without any URL validation or domain restrictions.

This can be used to target internal services (e.g. cloud metadata endpoints or internal HTTP APIs) reachable from the vLLM host.

------

Details

Vulnerable component

The vulnerable logic is in the batch runner entrypoint vllm/entrypoints/openai/run_batch.py, function download_bytes_from_url:

# run_batch.py Lines 442-482
async def download_bytes_from_url(url: str) -> bytes:
    """
    Download data from a URL or decode from a data URL.

    Args:
        url: Either an HTTP/HTTPS URL or a data URL (data:...;base64,...)

    Returns:
        Data as bytes
    """
    parsed = urlparse(url)
# Handle data URLs (base64 encoded)
    if parsed.scheme == "data":
# Format: data:...;base64,<base64_data>
        if "," in url:
            header, data = url.split(",", 1)
            if "base64" in header:
                return base64.b64decode(data)
            else:
                raise ValueError(f"Unsupported data URL encoding: {header}")
        else:
            raise ValueError(f"Invalid data URL format: {url}")
# Handle HTTP/HTTPS URLs
    elif parsed.scheme in ("http", "https"):
        async with (
            aiohttp.ClientSession() as session,
            session.get(url) as resp,
        ):
            if resp.status != 200:
                raise Exception(
                    f"Failed to download data from URL: {url}. Status: {resp.status}"
                )
            return await resp.read()

    else:
        raise ValueError(
            f"Unsupported URL scheme: {parsed.scheme}. "
            "Supported schemes: http, https, data"
        )

Key properties:

  • The function only parses the URL to dispatch on the scheme (data, http, https).
  • For http / https, it directly calls session.get(url) on the provided string.
  • There is no validation of:
  • hostname or IP address,
  • whether the target is internal or external,
  • port number,
  • path, query, or redirect target.
  • This is in contrast to the multimodal media path (MediaConnector), which implements an explicit domain allowlist. download_bytes_from_url does not reuse that protection.
URL controllability

The url argument is fully controlled by batch input JSON via the file_url field of BatchTranscriptionRequest / BatchTranslationRequest.

  1. Batch request body type:
# run_batch.py Line 67-80
class BatchTranscriptionRequest(TranscriptionRequest):
    """
    Batch transcription request that uses file_url instead of file.

    This class extends TranscriptionRequest but replaces the file field
    with file_url to support batch processing from audio files written in JSON format.
    """

    file_url: str = Field(
        ...,
        description=(
            "Either a URL of the audio or a data URL with base64 encoded audio data. "
        ),
    )
# run_batch.py Line 98-111
class BatchTranslationRequest(TranslationRequest):
    """
    Batch translation request that uses file_url instead of file.

    This class extends TranslationRequest but replaces the file field
    with file_url to support batch processing from audio files written in JSON format.
    """

    file_url: str = Field(
        ...,
        description=(
            "Either a URL of the audio or a data URL with base64 encoded audio data. "
        ),
    )

There is no restriction on the domain, IP, or port of file_url in these models.

  1. Batch input is parsed directly from the batch file:
# run_batch.py Line 139-179
class BatchRequestInput(OpenAIBaseModel):
    ...
    url: str
    body: BatchRequestInputBody
    @field_validator("body", mode="plain")
    @classmethod
    def check_type_for_url(cls, value: Any, info: ValidationInfo):
        url: str = info.data["url"]
        ...
        if url == "/v1/audio/transcriptions":
            return BatchTranscriptionRequest.model_validate(value)
        if url == "/v1/audio/translations":
            return BatchTranslationRequest.model_validate(value)
# run_batch.py Line 770-781
   logger.info("Reading batch from %s...", args.input_file)
# Submit all requests in the file to the engine "concurrently".
    response_futures: list[Awaitable[BatchRequestOutput]] = []
    for request_json in (await read_file(args.input_file)).strip().split("\n"):
# Skip empty lines.
        request_json = request_json.strip()
        if not request_json:
            continue

        request = BatchRequestInput.model_validate_json(request_json)

The batch runner reads each line of the input file (args.input_file), parses it as JSON, and constructs a BatchTranscriptionRequest / BatchTranslationRequest. Whatever file_url appears in that JSON line becomes batch_request_body.file_url.

  1. file_url is passed directly into download_bytes_from_url:
# run_batch.py Line 610-623
def wrapper(handler_fn: Callable):
        async def transcription_wrapper(
            batch_request_body: (BatchTranscriptionRequest | BatchTranslationRequest),
        ) -> (
            TranscriptionResponse
            | TranscriptionResponseVerbose
            | TranslationResponse
            | TranslationResponseVerbose
            | ErrorResponse
        ):
            try:
# Download data from URL
                audio_data = await download_bytes_from_url(batch_request_body.file_url)

So the data flow is:

  1. Attacker supplies JSON line in the batch input file with arbitrary body.file_url.
  2. BatchRequestInput / BatchTranscriptionRequest / BatchTranslationRequest parse that JSON and store file_url verbatim.
  3. make_transcription_wrapper calls download_bytes_from_url(batch_request_body.file_url).
  4. download_bytes_from_url’s HTTP/HTTPS branch issues aiohttp.ClientSession().get(url) to that attacker-controlled URL with no further validation.

This is a classic SSRF pattern: a server-side component makes arbitrary HTTP requests to a URL string taken from untrusted input.

Comparison with safer code

The project already contains a safer URL-handling path for multimodal media in vllm/multimodal/media/connector.py, which demonstrates the intent to mitigate SSRF via domain allowlists and URL normalization:

# connector.py Lines 169-189
 def load_from_url(
        self,
        url: str,
        media_io: MediaIO[_M],
        *,
        fetch_timeout: int | None = None,
    ) -> _M:
# type: ignore[type-var]
        url_spec = parse_url(url)

        if url_spec.scheme and url_spec.scheme.startswith("http"):
            self._assert_url_in_allowed_media_domains(url_spec)

            connection = self.connection
            data = connection.get_bytes(
                url_spec.url,
                timeout=fetch_timeout,
                allow_redirects=envs.VLLM_MEDIA_URL_ALLOW_REDIRECTS,
            )

            return media_io.load_bytes(data)

and:

# connector.py Lines 158-167
  def _assert_url_in_allowed_media_domains(self, url_spec: Url) -> None:
        if (
            self.allowed_media_domains
            and url_spec.hostname not in self.allowed_media_domains
        ):
            raise ValueError(
                f"The URL must be from one of the allowed domains: "
                f"{self.allowed_media_domains}. Input URL domain: "
                f"{url_spec.hostname}"
            )

download_bytes_from_url does not reuse this allowlist or any equivalent validation, even though it also fetches user-provided URLs.

AnalysisAI

Server-side request forgery (SSRF) in vLLM batch runner allows authenticated attackers to make arbitrary HTTP/HTTPS requests from the vLLM server by controlling the file_url field in batch input JSON, enabling targeting of internal services such as cloud metadata endpoints without URL validation or domain restrictions. The vulnerability affects vLLM's audio transcription and translation batch endpoints and is confirmed to have an upstream fix available via GitHub PR #38482 and commit 57861ae48d3493fa48b4d7d830b7ec9f995783e7. CVSS score is 5.4 (moderate); no public exploit code or confirmed active exploitation has been identified at time of analysis.

Technical ContextAI

The vulnerability resides in the download_bytes_from_url function in vllm/entrypoints/openai/run_batch.py (lines 442-482), which processes URLs provided via the file_url field of BatchTranscriptionRequest and BatchTranslationRequest objects. These request classes inherit from TranscriptionRequest and TranslationRequest respectively and are instantiated by parsing untrusted batch input JSON. The function dispatches on URL scheme (data, http, https) but performs no validation of hostname, IP address, port, path, query parameters, or redirect targets before issuing aiohttp.ClientSession().get(url) calls. The root cause (CWE-918: Server-Side Request Forgery) stems from the failure to implement domain allowlisting or URL normalization that the project itself demonstrates in safer code paths (vllm/multimodal/media/connector.py uses _assert_url_in_allowed_media_domains). The vLLM batch runner accepts JSON-formatted batch requests where each line is parsed directly into BatchRequestInput, making file_url fully attacker-controllable when an attacker can influence batch input files.

RemediationAI

Vendor-released patch is available via upstream fix PR #38482 (commit 57861ae48d3493fa48b4d7d830b7ec9f995783e7). Users should upgrade vLLM to a patched release version that includes this commit. The fix implements URL validation similar to the existing MediaConnector allowlist mechanism: validate hostnames and domains against an allowed list before issuing HTTP requests in the download_bytes_from_url function. Immediate workarounds include restricting access to batch processing endpoints to trusted users only, validating and sanitizing batch input JSON files before submission to vLLM (ensuring file_url fields reference only external or explicitly approved domains), and deploying vLLM in network isolation such that the batch runner cannot reach sensitive internal services (e.g., cloud metadata endpoints). For detailed remediation guidance, refer to the GitHub Security Advisory at https://github.com/advisories/GHSA-pf3h-qjgv-vcpr and the patch PR at https://github.com/vllm-project/vllm/pull/38482.

Vendor StatusVendor

Share

CVE-2026-34753 vulnerability details – vuln.today

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy