CVE-2026-27604: FOSSBilling is a free, open-source billing and client management system

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CRITICAL 10.0REMOTE

CVE-2026-27604 is a critical-severity flaw (CVSS 10.0) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 avail

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.3% (top 30%)
CISA exploited list	No
Weakness	CWE-200, CWE-306, CWE-862, CWE-863
Published	2026-06-23
Last modified	2026-06-23

Publisher (CNA): GitHub, Inc.

Last updated 2026-06-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-06-23 15:16 UTCPublished CVE record published
2026-06-23 16:16 UTCUpdated Record last modified

Exact fixes by distribution

Fedora 46 · python3.11 · FIXED · 3.11.18-1.fc46 · FEDORA-2026-cc775894f4 · source

sudo dnf upgrade --advisory=FEDORA-2026-cc775894f4

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-57mv-jm88-66jc
Write-up: www.vulncheck.com/blog/fossbilling-auth-bypass-ssti-rce
Nuclei scan template: FOSSBilling 0.5.4-0.7.x - Unauthenticated System API Role Authorization Bypass

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-27604?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-27604 being exploited?

CVE-2026-27604 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-27604 affect?

CVE-2026-27604 affects affected software. Severity is critical (CVSS 10.0). 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/*` endp

How urgent is CVE-2026-27604?

Priority 60/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

References

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