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TI-2026-76427 Aliases CVE-2026-111053

Path traversal in FOSSBilling reveals whether arbitrary files exist

Priority LOW 37CWE-200Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Information disclosure
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-200.

Summary

FOSSBilling from 0.1.0 before 0.8.7 has a path traversal flaw (CWE-22) in the unauthenticated guest/system/template_exists endpoint. The file parameter is joined to the theme path without rejecting .. sequences or checking that the result stays inside the theme directory. A remote attacker can send traversal sequences and read the returned boolean to learn whether arbitrary files or directories exist, without disclosing file contents.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

FOSSBilling is an open source billing and client-management platform. From 0.1.0 until 0.8.7, the unauthenticated api/guest/system/template_exists endpoint permits path traversal because templateExists uses Path::join on the attacker-controlled file parameter without rejecting .. sequences or verifying that the resolved path remains inside the active theme directory. The trigger is an unauthenticated request to guest/system/template_exists containing traversal sequences in the file parameter. An attacker can submit traversal sequences in the file parameter and observe the returned boolean to determine whether arbitrary files or directories exist on the server. The oracle does not disclose file contents. This issue is fixed in version 0.8.7.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00368 30th percentileScored 2026-11-07
Fix Fixed FOSSBilling (FOSSBilling): 0.8.7

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
FOSSBillingFOSSBilling0.1.0 to before 0.8.70.8.7Patch availableCNA
  • FOSSBilling VendorFOSSBilling Affected 0.1.0 to before 0.8.7 Fixed in 0.8.7 Patch available CNA

Remediation

Upgrade FOSSBilling to version 0.8.7, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA FOSSBilling (FOSSBilling) Fixed in 0.8.7

Timeline

  1. 2026-10-19 Threatist record created from CVE-2026-111053

References

Other 4

  • TI-2023-03258 SQL Injection in fossbilling/fossbilling CVSS 3.1CRITICAL 9.8
  • TI-2023-03719 Insufficient Session Expiration in fossbilling/fossbilling CVSS 3.1CRITICAL 9.8
  • TI-2023-03259 Unrestricted Upload of File with Dangerous Type in fossbilling/fossbilling CVSS 3.1HIGH 8.8
  • TI-2023-03261 Improper Neutralization of Formula Elements in a CSV File in fossbilling/fossbilling CVSS 3.1HIGH 8.0
  • TI-2026-30636 FOSSBilling missing authorization in guest Invoice API endpoints CVSS 4.0HIGH 7.7
  • TI-2023-03173 Code Injection in fossbilling/fossbilling CVSS 3.1HIGH 7.2
See all 43 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences