CVE-2026-57449 Actual Sync Server: CORS Proxy GitHub API Allowlist Prefix Bypass Leaks Private Repositories Through the Server GitHub Token
Authenticated users can bypass CORS proxy allowlists to read private GitHub repositories using the server's token due to a prefix matching flaw.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-57449?
CVE-2026-57449 is a high-severity vulnerability in actualbudget actual, published on 25 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Actual is a local-first personal finance tool. Prior to 26.7.0, Actual Sync Server's CORS proxy is intended to let authenticated users fetch resources only from repositories listed in the official plugin allowlist. When `ACTUAL_GITHUB_TOKEN` is configured, the proxy automatically attaches the server's GitHub token to GitHub requests. The GitHub API allowlist check uses a raw `startsWith()` prefix test for `/repos/{owner}/{repo}` without requiring a path boundary after the repository name. If an allowlisted public plugin repository is `https://github.com/acme/plugin`, the proxy also accepts GitHub API URLs. Those URLs are outside the allowlisted repository but still pass because their API path starts with `/repos/acme/plugin`. The proxy then forwards the request with the server's `ACTUAL_GITHUB_TOKEN`, allowing any authenticated Actual user to read private GitHub resources reachable by that token. Version 26.7.0 fixes the issue.
Which versions are affected by CVE-2026-57449?
2 open source packages ship an affected version, including @actual-app/sync-server.
| Package | Affected | Fixed in |
|---|---|---|
@actual-app/sync-server npm | All versions | 26.7.0 |
@actual-app/sync-server npm | All versions | 26.7.0 |
How do I fix CVE-2026-57449?
Upgrade @actual-app/sync-server to 26.7.0 or later.
Is CVE-2026-57449 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-57449 exists.
Sources
Also known as GHSA-m62c-5q34-f3cf.