CVE-2026-42604Network attack vector

OAuth2 client secret disclosure via misguarded OpenID endpoint

Published Jun 12, 2026 · Updated Jun 12, 2026

Incorrect authorization in Actual sync-server before 26.5.0 allows remote attackers to disclose an OAuth2 client secret via POST /openid/config. The handler accepts the bootstrap password as its only guard and returns the full stored OpenID Connect configuration, including client_secret, without an authenticated session or rate limiting. Network access to an OpenID-enabled server is required; brute-forcing the bootstrap password exposes credentials that permit application impersonation to the identity provider.

CVSS severityUnavailable
Unscored
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Actual sync-server before 26.5.0 allows remote attackers to disclose an OAuth2 client secret via POST /openid/config. The handler accepts the bootstrap password as its only guard and returns the full stored OpenID Connect configuration, including client_secret, without an authenticated session or rate limiting. Network access to an OpenID-enabled server is required; brute-forcing the bootstrap password exposes credentials that permit application impersonation to the identity provider.

The record

CVE
CVE-2026-42604
Published
Jun 12, 2026
Updated
Jun 12, 2026
Vendor
Actual Budget
Product
Actual
Classifications
CWE-863, T1110
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 26.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Actual Budget · Actualversion=< 26.5.0

Published CVSS scores

6.9GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1110Brute Force

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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