CVE-2026-42604: Actual has an OpenID `client_secret` Disclosure via Broken Authorization Guard in `/openid/config`

Severity: medium (CVSS 6.9 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-12 · updated 2026-10-26
Weakness: CWE-863

Description

Actual is a local-first personal finance tool. The `POST /openid/config` endpoint in Actual Budget's sync-server versions <= 26.4.0 exposes the full OpenID Connect configuration—including the OAuth2 `client_secret`—to any caller who knows the bootstrap password. The endpoint also lacks authentication and rate limiting, making the bootstrap password brute-forceable. Version 26.5.0 fixes the issue.

Affected products

actualbudget actual: before 26.5.0

References

https://actualbudget.org/blog/release-26.5.0
https://github.com/actualbudget/actual/security/advisories/GHSA-49v6-pqjq-xw55

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