How severe is CVE-2026-27604?

CVE-2026-27604 has a CVSS 4.0 base score of 10.0, rated critical severity.

Is CVE-2026-27604 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-27604?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-27604 have an EU (EUVD) identifier?

Yes. CVE-2026-27604 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38451.

When was CVE-2026-27604 published?

CVE-2026-27604 was published on 2026-06-23.

CVE-2026-27604

CVE-2026-27604 is a critical-severity vulnerability with a CVSS 4.0 base score of 10.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-200.

Key facts

Severity: Critical (CVSS 4.0 base score 10.0)
EPSS exploit prediction: 0% (33rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38451
Weakness: CWE-200
Published: 2026-06-23
Last modified: 2026-06-23

Description

FOSSBilling is a free, open-source billing and client management system. Starting in version 0.5.4 and prior to version 0.8.0, an authorization bypass in the API role handling allows unauthenticated access to privileged `/api/system/*` endpoints. Because `system` resolves to the cron admin identity, attackers can invoke admin API methods without valid credentials, session, or CSRF token. Version 0.8.0 patches the issue. Some workarounds are available. Block external access to `/api/system/*` at reverse proxy/WAF, restrict API access by trusted source IPs only (`api.allowed_ips`), rotate all admin/client API tokens immediately, invalidate active sessions and reset high-privilege credentials, and/or review API request logs for suspicious `/api/system/` access and treat as potential incident.

Frequently asked questions

What is CVE-2026-27604?: FOSSBilling is a free, open-source billing and client management system. Starting in version 0.5.4 and prior to version 0.8.0, an authorization bypass in the API role handling allows unauthenticated access to privileged `/api/system/*` endpoints. Because `system` resolves to the cron admin identity, attackers can invoke admin API methods without valid credentials, session, or CSRF token. Version 0.8.0 patches the issue. Some workarounds are available. Block external access to `/api/system/*` at reverse proxy/WAF, restrict API access by trusted source IPs only (`api.allowed_ips`), rotate all admin/client API tokens immediately, invalidate active sessions and reset high-privilege credentials, and/or review API request logs for suspicious `/api/system/` access and treat as potential incident.
How severe is CVE-2026-27604?: CVE-2026-27604 has a CVSS 4.0 base score of 10.0, rated critical severity.
Is CVE-2026-27604 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-27604?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-27604 have an EU (EUVD) identifier?: Yes. CVE-2026-27604 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38451.
When was CVE-2026-27604 published?: CVE-2026-27604 was published on 2026-06-23.

References

Other CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) vulnerabilities

CVE-2026-40965 — Critical (CVSS 10.0): Cloud Foundry UAA versions v76.12.0 through v78.12.0 are vulnerable to a private key exposure. The server contains a…
CVE-2026-42826 — Critical (CVSS 10.0): Exposure of sensitive information to an unauthorized actor in Azure DevOps allows an unauthorized attacker to disclose…
CVE-2025-29270 — Critical (CVSS 10.0): Incorrect access control in the realtime.cgi endpoint of Deep Sea Electronics devices DSE855 v1.1.0 to v1.1.26 allows…
CVE-2025-61481 — Critical (CVSS 10.0): An issue in MikroTik RouterOS v.7.14.2 and SwOS v.2.18 exposes the WebFig management interface over cleartext HTTP by…
CVE-2025-53624 — Critical (CVSS 10.0): The Docusaurus gists plugin adds a page to your Docusaurus instance, displaying all public gists of a GitHub user.…
CVE-2025-22612 — Critical (CVSS 10.0): Coolify is an open-source and self-hostable tool for managing servers, applications, and databases. Prior to version…

Browse all CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) vulnerabilities →