CVE-2026-43920
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedFOSSBilling is a free, open-source billing and client management system. In versions 0.5.4 through 0.7.2, the /run-patcher maintenance endpoint in FOSSBilling was accessible without authentication, which allowed unauthenticated remote users to trigger update patch routines that modify configuration files, execute database schema changes, perform filesystem mutations, and clear caches. The /run-patcher endpoint executes privileged maintenance operations - configuration migrations, database patch execution (including ALTER TABLE, DROP TABLE, UPDATE statements), filesystem deletions and renames, and cache clearing - without requiring administrator authentication, CSRF validation, or CLI context. An unauthenticated remote attacker can trigger these operations by sending a simple HTTP GET request to /run-patcher, which can be abused for denial-of-service attacks. Certain patches (e.g., batch token regeneration for all admin and client accounts in patch 53, and session invalidation) are disruptive even when re-executed against an already-patched instance. Repeated or concurrent requests may also cause inconsistent database state. This issue has been fixed in version 0.8.0.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFOSSBilling versions 0.5.4-0.7.2 contain an unauthenticated command injection vulnerability in the /run-patcher maintenance endpoint. This endpoint executes privileged operations including database schema changes (ALTER TABLE, DROP TABLE, UPDATE), configuration file modifications, filesystem mutations, cache clearing, and batch token regeneration without requiring authentication, CSRF validation, or CLI context. An attacker can trigger these destructive operations via a simple HTTP GET request.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify FOSSBilling installationLocate the FOSSBilling installation directory. Common paths include /var/www/fossbilling, /var/www/html/fossbilling, or the document root of the web server. Look for the src/Version.php file or a composer.json file that contains the version declaration.Affected if FOSSBilling is installed on the system and the version cannot be determined or falls within 0.5.4 to 0.7.2.
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Determine installed FOSSBilling versionOpen the version file (typically src/Version.php or similar) and read the version number. Alternatively, check the composer.json file for the 'version' field or the release metadata.Affected if The installed version is 0.5.4, 0.5.5, 0.5.6, 0.5.7, 0.5.8, 0.6.0, 0.6.1, 0.7.0, 0.7.1, or 0.7.2.
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Verify /run-patcher endpoint accessibilitySend an HTTP GET request to the /run-patcher endpoint on the FOSSBilling server (e.g., curl -k -s -o /dev/null -w '%{http_code}' https://TARGET/fossbilling/index.php/_run_patcher or similar path). The endpoint may require a GET parameter or may respond to any request.Affected if The endpoint returns an HTTP 200 response, indicating it is accessible without authentication.
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Check for recent patcher execution logsReview web server access logs and FOSSBilling application logs for requests to /run-patcher, _run_patcher, or similar maintenance endpoints. Look for unexpected or unauthorized access patterns.Affected if Evidence exists of requests to the patcher endpoint from unexpected IP addresses or at unexpected times.
The environment is affected if FOSSBilling version 0.5.4 through 0.7.2 is installed and the /run-patcher maintenance endpoint is accessible without authentication.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade FOSSBilling to version 0.8.0 or later. If immediate upgrade is not feasible, disable or restrict access to the /run-patcher endpoint at the web server level until the upgrade can be applied.
0.8.0
- 1. Create a complete backup of the FOSSBilling database and all application files
- 2. Download FOSSBilling version 0.8.0 from the official repository (github.com)
- 3. Replace the existing FOSSBilling installation files with the version 0.8.0 files
- 4. Run any database migration scripts included in the upgrade if applicable
- 5. Verify the /run-patcher endpoint now requires authentication by attempting an unauthenticated request
- 6. Confirm normal administrative login and functionality work after upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation3.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-43920 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-43920 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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