CVE-2026-30870 — @powersync/service-core
MEDIUMCVE-2026-30870 is a medium-severity (CVSS 6.5) CWE-285 vulnerability in @powersync/service-core. A fix is available for @powersync/service-core — see the affected versions and patch details below.
Some sync filters in PowerSync Service ignored using `config.edition: 3`
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-30870.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-30870 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@powersync/service-corenpm@powersync/service-sync-rulesnpmDescription
Impact
In version 1.20.0, when using new sync streams with config.edition: 3, certain subquery filters were ignored when determining which data to sync to users.
Depending on the sync stream configuration, this could result in authenticated users syncing data that should have been restricted.
Only queries that gate synchronization using subqueries without partitioning the result set are affected.
Not affected:
- Sync rules (bucket_definitions)
- Sync streams using
config.edition: 2 - No data is exposed without authenticating
Patches
The issue is fixed in 1.20.1. Restarting the service with the new version is sufficient - no reprocessing of sync streams is required.
Any data that users erroneously synced will be automatically removed from those devices when they connect again.
We have updated all affected PowerSync Cloud instances to the fixed version, and are reaching out to affected customers.
For self-hosted PowerSync instances, update to the latest version and restart.
Affected queries
Subqueries used only to determine whether or not a table should be synced (without partitioning the data itself) are affected. Examples:
-- Goal: Sync a table only to admin users
-- 1.20.0: all authenticated users would sync this table
SELECT * FROM sensitive_table WHERE auth.user_id() IN (SELECT user_id FROM admins)
SELECT * FROM sensitive_table WHERE 1 IN (SELECT 1 FROM users WHERE id = auth.user_id() AND is_admin = TRUE)
-- Goal: Sync a table only if authorized
-- 1.20.0: all authenticated users would sync this table
SELECT * FROM sensitive_table WHERE 'sensitive_table' IN (SELECT table_name FROM synced_table WHERE "user" = auth.user_id())
SELECT * FROM sensitive_table WHERE 'sensitive_table' IN auth.parameter('allowed_tables')
Queries that partition data (for example SELECT * FROM sensitive_table WHERE owner IN (SELECT id FROM users WHERE is_admin AND id = auth.user_id())) are not affected by this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @powersync/service-core | ≥ 1.20.0&&< 1.20.1 | 1.20.1npm install @powersync/service-core@1.20.1 |
| 📦npm | @powersync/service-sync-rules | ≥ 0.32.0&&< 0.33.0 | 0.33.0npm install @powersync/service-sync-rules@0.33.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @powersync/service-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @powersync/service-core to 1.20.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30870 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-30870 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-30870. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-30870 in your dependencies?
O3 Security finds CVE-2026-30870 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.