# CVE-2026-27638: ActualBudget missing authorization in sync endpoints allows cross-user budget file access in multi-user mode

> In multi-user mode, authenticated users can access and modify other users' budget files due to missing ownership checks on sync endpoints.

- **Severity:** Medium 5.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P`)
- **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:** 26 Feb 2026
- **Updated:** 2 Mar 2026
- **Also known as:** GHSA-qmjj-p7m9-wjrv

## What is CVE-2026-27638?

CVE-2026-27638 is a medium-severity missing authorization vulnerability in actualbudget actual, published on 26 Feb 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 version 26.2.1, in multi-user mode (OpenID), the sync API endpoints (`/sync/*`) don't verify that the authenticated user owns or has access to the file being operated on. Any authenticated user can read, modify, and overwrite any other user's budget files by providing their file ID. Version 26.2.1 patches the issue.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-27638?

2 open source packages ship an affected version, including @actual-app/sync-server. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@actual-app/sync-server` | npm | All versions | 26.2.1 |
| `@actual-app/sync-server` | npm | All versions | 26.2.1 |

Products: Actualbudget Actual.

## How do I fix CVE-2026-27638?

Upgrade @actual-app/sync-server to 26.2.1 or later.

## Is CVE-2026-27638 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27638 exists.

## Other vulnerabilities in actualbudget actual

- [CVE-2026-27584](https://insights.sbomify.com/CVE-2026-27584/): ActualBudget server is Missing Authentication for SimpleFIN and Pluggy AI bank sync endpoints (critical 9.2)
- [CVE-2026-33318](https://insights.sbomify.com/CVE-2026-33318/): Actual has Privilege Escalation via 'change-password' Endpoint on OpenID-Migrated Servers (high 8.8)
- [CVE-2026-3089](https://insights.sbomify.com/CVE-2026-3089/): Actual Sync Server 26.2.1 - Authenticated Path Traversal (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27638 and fix it if it is affected.

What it is: CVE-2026-27638 is a medium-severity missing authorization vulnerability in actualbudget actual, published on 26 Feb 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-2026-27638 exists.

Affected packages and fixed versions:
- @actual-app/sync-server (npm): affected all versions; fixed in 26.2.1
- @actual-app/sync-server (npm): affected all versions; fixed in 26.2.1

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-2026-27638/ (Markdown: https://insights.sbomify.com/CVE-2026-27638/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27638
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27638
- OSV: https://osv.dev/vulnerability/CVE-2026-27638

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27638/
Summaries are generated and may contain mistakes; the official description above is the record.