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Update dependency starlette to ^0.49.0 [SECURITY] #316

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Update dependency starlette to ^0.49.0 [SECURITY] #316

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This PR contains the following updates:

Package Change Age Confidence
starlette (changelog) ^0.38.0 -> ^0.49.0 age confidence

GitHub Vulnerability Alerts

CVE-2024-47874

Summary

Starlette treats multipart/form-data parts without a filename as text form fields and buffers those in byte strings with no size limit. This allows an attacker to upload arbitrary large form fields and cause Starlette to both slow down significantly due to excessive memory allocations and copy operations, and also consume more and more memory until the server starts swapping and grinds to a halt, or the OS terminates the server process with an OOM error. Uploading multiple such requests in parallel may be enough to render a service practically unusable, even if reasonable request size limits are enforced by a reverse proxy in front of Starlette.

PoC

from starlette.applications import Starlette
from starlette.routing import Route

async def poc(request):
    async with request.form():
        pass

app = Starlette(routes=[
    Route('/', poc, methods=["POST"]),
])
curl http://localhost:8000 -F 'big=</dev/urandom'

Impact

This Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests.

CVE-2025-54121

Summary

When parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means we can't accept new connections.

Details

Please see this discussion for details: https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403. In summary the following UploadFile code (copied from here) has a minor bug. Instead of just checking for self._in_memory we should also check if the additional bytes will cause a rollover.

    @&#8203;property
    def _in_memory(self) -> bool:
        # check for SpooledTemporaryFile._rolled
        rolled_to_disk = getattr(self.file, "_rolled", True)
        return not rolled_to_disk

    async def write(self, data: bytes) -> None:
        if self.size is not None:
            self.size += len(data)

        if self._in_memory:
            self.file.write(data)
        else:
            await run_in_threadpool(self.file.write, data)

I have already created a PR which fixes the problem: https://github.com/encode/starlette/pull/2962

PoC

See the discussion here for steps on how to reproduce.

Impact

To be honest, very low and not many users will be impacted. Parsing large forms is already CPU intensive so the additional IO block doesn't slow down starlette that much on systems with modern HDDs/SSDs. If someone is running on tape they might see a greater impact.

CVE-2025-62727

Summary

An unauthenticated attacker can send a crafted HTTP Range header that triggers quadratic-time processing in Starlette's FileResponse Range parsing/merging logic. This enables CPU exhaustion per request, causing denial‑of‑service for endpoints serving files (e.g., StaticFiles or any use of FileResponse).

Details

Starlette parses multi-range requests in FileResponse._parse_range_header(), then merges ranges using an O(n^2) algorithm.

# starlette/responses.py
_RANGE_PATTERN = re.compile(r"(\d*)-(\d*)") # vulnerable to O(n^2) complexity ReDoS

class FileResponse(Response):
    @&#8203;staticmethod
    def _parse_range_header(http_range: str, file_size: int) -> list[tuple[int, int]]:
        ranges: list[tuple[int, int]] = []
        try:
            units, range_ = http_range.split("=", 1)
        except ValueError:
            raise MalformedRangeHeader()

        # [...]

        ranges = [
            (
                int(_[0]) if _[0] else file_size - int(_[1]),
                int(_[1]) + 1 if _[0] and _[1] and int(_[1]) < file_size else file_size,
            )
            for _ in _RANGE_PATTERN.findall(range_) # vulnerable
            if _ != ("", "")
        ]

The parsing loop of FileResponse._parse_range_header() uses the regular expression which vulnerable to denial of service for its O(n^2) complexity. A crafted Range header can maximize its complexity.

The merge loop processes each input range by scanning the entire result list, yielding quadratic behavior with many disjoint ranges. A crafted Range header with many small, non-overlapping ranges (or specially shaped numeric substrings) maximizes comparisons.

This affects any Starlette application that uses:

  • starlette.staticfiles.StaticFiles (internally returns FileResponse) — starlette/staticfiles.py:178
  • Direct starlette.responses.FileResponse responses

PoC

#!/usr/bin/env python3

import sys
import time

try:
    import starlette
    from starlette.responses import FileResponse
except Exception as e:
    print(f"[ERROR] Failed to import starlette: {e}")
    sys.exit(1)

def build_payload(length: int) -> str:
    """Build the Range header value body: '0' * num_zeros + '0-'"""
    return ("0" * length) + "a-"

def test(header: str, file_size: int) -> float:
    start = time.perf_counter()
    try:
        FileResponse._parse_range_header(header, file_size)
    except Exception:
        pass
    end = time.perf_counter()
    elapsed = end - start
    return elapsed

def run_once(num_zeros: int) -> None:
    range_body = build_payload(num_zeros)
    header = "bytes=" + range_body
    # Use a sufficiently large file_size so upper bounds default to file size
    file_size = max(len(range_body) + 10, 1_000_000)
    
    print(f"[DEBUG] range_body length: {len(range_body)} bytes")
    elapsed_time = test(header, file_size)
    print(f"[DEBUG] elapsed time: {elapsed_time:.6f} seconds\n")

if __name__ == "__main__":
    print(f"[INFO] Starlette Version: {starlette.__version__}")
    for n in [5000, 10000, 20000, 40000]:
        run_once(n)

"""
$ python3 poc_dos_range.py
[INFO] Starlette Version: 0.48.0
[DEBUG] range_body length: 5002 bytes
[DEBUG] elapsed time: 0.053932 seconds

[DEBUG] range_body length: 10002 bytes
[DEBUG] elapsed time: 0.209770 seconds

[DEBUG] range_body length: 20002 bytes
[DEBUG] elapsed time: 0.885296 seconds

[DEBUG] range_body length: 40002 bytes
[DEBUG] elapsed time: 3.238832 seconds
"""

Impact

Any Starlette app serving files via FileResponse or StaticFiles; frameworks built on Starlette (e.g., FastAPI) are indirectly impacted when using file-serving endpoints. Unauthenticated remote attackers can exploit this via a single HTTP request with a crafted Range header.

Release Notes

Kludex/starlette (starlette)

v0.49.1: Version 0.49.1

Compare Source

This release fixes a security vulnerability in the parsing logic of the Range header in FileResponse.

You can view the full security advisory: GHSA-7f5h-v6xp-fcq8

Fixed

Full Changelog: Kludex/starlette@0.49.0...0.49.1

v0.49.0: Version 0.49.0

Compare Source

Added

  • Add encoding parameter to Config class #​2996.
  • Support multiple cookie headers in Request.cookies #​3029.
  • Use Literal type for WebSocketEndpoint encoding values #​3027.

Changed

  • Do not pollute exception context in Middleware when using BaseHTTPMiddleware #​2976.

New Contributors

Full Changelog: Kludex/starlette@0.48.0...0.49.0

v0.48.0: Version 0.48.0

Compare Source

Added

  • Add official Python 3.14 support #​3013.

Changed

New Contributors

Full Changelog: Kludex/starlette@0.47.3...0.48.0

v0.47.3: Version 0.47.3

Compare Source

Fixed

New Contributors

Full Changelog: Kludex/starlette@0.47.2...0.47.3

v0.47.2

Compare Source

Fixed

  • Make UploadFile check for future rollover #​2962.

New Contributors

Full Changelog: Kludex/starlette@0.47.1...0.47.2

v0.47.1: Version 0.47.1

Compare Source

Fixed

  • Use Self in TestClient.__enter__ #​2951
  • Allow async exception handlers to type-check #​2949

Full Changelog: Kludex/starlette@0.47.0...0.47.1

v0.47.0: Version 0.47.0

Compare Source

Added

  • Add support for ASGI pathsend extension #​2671.
  • Add partitioned attribute to Response.set_cookie #​2501.

Changed

  • Change methods parameter type from list[str] to Collection[str] #​2903.
  • Replace import typing by from typing import ... in the whole codebase #​2867.

Fixed

  • Mark ExceptionMiddleware.http_exception as async to prevent thread creation #​2922.

New Contributors

Full Changelog: Kludex/starlette@0.46.2...0.47.0

v0.46.2: Version 0.46.2

Compare Source

What's Changed

New Contributors

Full Changelog: Kludex/starlette@0.46.1...0.46.2

v0.46.1: Version 0.46.1

Compare Source

Fixed

  • Allow relative directory path when follow_symlinks=True #​2896.

Full Changelog: Kludex/starlette@0.46.0...0.46.1

v0.46.0: Version 0.46.0

Compare Source

Added

  • GZipMiddleware: Make sure Vary header is always added if a response can be compressed #​2865.

Fixed

  • Raise exception from background task on BaseHTTPMiddleware #​2812.
  • GZipMiddleware: Don't compress on server sent events #​2871.

Changed

  • MultiPartParser: Rename max_file_size to spool_max_size #​2780.

Deprecated

  • Add deprecated warning to TestClient(timeout=...) #​2840.

New Contributors

Full Changelog: Kludex/starlette@0.45.3...0.46.0

v0.45.3: Version 0.45.3

Compare Source

Fixed

Full Changelog: Kludex/starlette@0.45.2...0.45.3

v0.45.2: Version 0.45.2

Compare Source

Fixed
  • Make create_memory_object_stream compatible with old anyio versions once again, and bump anyio minimum version to 3.6.2 by @​graingert in #​2833.

Full Changelog: Kludex/starlette@0.45.1...0.45.2

v0.45.1: Version 0.45.1

Compare Source

Fixed
Refactor

Full Changelog: Kludex/starlette@0.45.0...0.45.1

v0.45.0: Version 0.45.0

Compare Source

Removed

Full Changelog: Kludex/starlette@0.44.0...0.45.0

v0.44.0: Version 0.44.0

Compare Source

Added

New Contributors

Full Changelog: Kludex/starlette@0.43.0...0.44.0

v0.43.0: Version 0.43.0

Compare Source

Removed

  • Remove deprecated allow_redirects argument from TestClient #​2808.

Added

  • Make UUID path parameter conversion more flexible #​2806.

New Contributors

Full Changelog: Kludex/starlette@0.42.0...0.43.0

v0.42.0: Version 0.42.0

Compare Source

Added

  • Raise ClientDisconnect on StreamingResponse #​2732.

Fixed

  • Use ETag from headers when parsing If-Range in FileResponse #​2761.
  • Follow directory symlinks in StaticFiles when follow_symlinks=True #​2711.
  • Bump minimum python-multipart version to 0.0.18 0ba8395.
  • Bump minimum httpx version to 0.27.0 #​2773.

New Contributors

Full Changelog: Kludex/starlette@0.41.3...0.42.0

v0.41.3: Version 0.41.3

Compare Source

Fixed

  • Exclude the query parameters from the scope[raw_path] on the TestClient #​2716.
  • Replace dict by Mapping on HTTPException.headers #​2749.
  • Correct middleware argument passing and improve factory pattern #​2752.

Full Changelog: Kludex/starlette@0.41.2...0.41.3

v0.41.2: Version 0.41.2

Compare Source

What's Changed

Full Changelog: Kludex/starlette@0.41.1...0.41.2

v0.41.1: Version 0.41.1

Compare Source

What's Changed

Full Changelog: Kludex/starlette@0.41.0...0.41.1

v0.41.0: Version 0.41.0

Compare Source

Added

  • Allow to raise HTTPException before websocket.accept() encode#2725

v0.40.0: Version 0.40.0

Compare Source

This release fixes a Denial of service (DoS) via multipart/form-data requests.

You can view the full security advisory:
GHSA-f96h-pmfr-66vw

Fixed

  • Add max_part_size to MultiPartParser to limit the size of parts in multipart/form-data
    requests fd038f3.

v0.39.2: Version 0.39.2

Compare Source

Fixed

  • Allow use of request.url_for when only "app" scope is available #​2672.
  • Fix internal type hints to support python-multipart==0.0.12 #​2708.

Full Changelog: Kludex/starlette@0.39.1...0.39.2

v0.39.1: Version 0.39.1

Compare Source

Fixed

  • Avoid regex re-compilation in responses.py and schemas.py #​2700.
  • Improve performance of get_route_path by removing regular expression usage #​2701.
  • Consider FileResponse.chunk_size when handling multiple ranges #​2703.
  • Use token_hex for generating multipart boundary strings #​2702.

Full Changelog: Kludex/starlette@0.39.0...0.39.1

v0.39.0: Version 0.39.0

Compare Source

Added

  • Add support for HTTP Range to FileResponse #​2697

Full Changelog: Kludex/starlette@0.38.6...0.39.0

v0.38.6: Version 0.38.6

Compare Source

Fixed

  • Close unclosed MemoryObjectReceiveStream in TestClient #​2693.

Full Changelog: Kludex/starlette@0.38.5...0.38.6

v0.38.5: Version 0.38.5

Compare Source

Fixed

  • Schedule BackgroundTasks from within BaseHTTPMiddleware #​2688.
    This behavior was removed in 0.38.3, and is now restored.

Full Changelog: Kludex/starlette@0.38.4...0.38.5

v0.38.4: Version 0.38.4

Compare Source

Fixed

  • Ensure accurate root_path removal in get_route_path function #​2600

Full Changelog: Kludex/starlette@0.38.3...0.38.4

v0.38.3: Version 0.38.3

Compare Source

Added
Fixed
  • Don't poll for disconnects in BaseHTTPMiddleware via StreamingResponse #​2620.

Full Changelog: Kludex/starlette@0.38.2...0.38.3

v0.38.2: Version 0.38.2

Compare Source

Fixed

  • Fix routing.get_name() not to assume all routines have __name__ #​2648

Full Changelog: Kludex/starlette@0.38.1...0.38.2

v0.38.1: Version 0.38.1

Compare Source

Removed

  • Revert "Add support for ASGI pathsend extension" #​2649.

Full Changelog: Kludex/starlette@0.38.0...0.38.1

Configuration

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This PR was generated by Mend Renovate. View the repository job log.

@renovate renovate bot requested a review from ks129 as a code owner October 15, 2024 19:18
@renovate renovate bot force-pushed the renovate/pypi-starlette-vulnerability branch 2 times, most recently from 1c29c1d to 9b996d5 Compare June 6, 2025 02:34
@renovate renovate bot force-pushed the renovate/pypi-starlette-vulnerability branch from 9b996d5 to 79f6a6a Compare July 21, 2025 23:31
@renovate renovate bot changed the title Update dependency starlette to ^0.40.0 [SECURITY] Update dependency starlette to ^0.47.0 [SECURITY] Jul 21, 2025
@renovate renovate bot force-pushed the renovate/pypi-starlette-vulnerability branch from 79f6a6a to e9f6bbf Compare July 22, 2025 19:56
@renovate renovate bot force-pushed the renovate/pypi-starlette-vulnerability branch from e9f6bbf to 7f751a1 Compare August 9, 2025 00:44
@renovate
Update dependency starlette to ^0.49.0 [SECURITY]
1400967 
| datasource | package   | from   | to     |
| ---------- | --------- | ------ | ------ |
| pypi       | starlette | 0.38.0 | 0.49.1 |
@renovate renovate bot force-pushed the renovate/pypi-starlette-vulnerability branch from 7f751a1 to 1400967 Compare October 28, 2025 22:09
@renovate renovate bot changed the title Update dependency starlette to ^0.47.0 [SECURITY] Update dependency starlette to ^0.49.0 [SECURITY] Oct 28, 2025
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