# 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.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** GHSA-m62c-5q34-f3cf

## 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.

Weakness: CWE-863 (Incorrect Authorization), CWE-284 (Improper Access Control), CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2026-57449?

2 open source packages ship an affected version, including @actual-app/sync-server.


| Package | Ecosystem | 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57449 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-57449 exists.

Affected packages and fixed versions:
- @actual-app/sync-server (npm): affected all versions; fixed in 26.7.0
- @actual-app/sync-server (npm): affected all versions; fixed in 26.7.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-57449/ (Markdown: https://insights.sbomify.com/CVE-2026-57449/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57449
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57449
- OSV: https://osv.dev/vulnerability/CVE-2026-57449

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-57449/
Summaries are generated and may contain mistakes; the official description above is the record.