CVE-2026-43926: FOSSBilling's password reset confirmation endpoint lacks rate limiting

Description

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, the password reset confirmation endpoint `/client/reset-password-confirm/:hash` is handled by a non-API controller and is not covered by FOSSBilling's rate limiter, which only applies to `/api/*` routes. This allows an attacker to probe the endpoint for valid reset tokens without any per-IP request limiting, attempt counting, or lockout mechanism. The endpoint acts as an oracle, returning a distinguishable response for valid versus invalid tokens (HTTP 200 vs HTTP 302 redirect). An attacker can submit unlimited token guesses to the password reset confirmation endpoint with no throttling applied. However, practical exploitability is significantly mitigated by the current token generation, which uses `hash('sha256', random_bytes(32))`, providing 256 bits of entropy. Tokens also expire after 15 minutes and are deleted after successful use. The same architectural gap applies to other controller-served auth routes, including `/staff/email/:hash` (admin password reset confirmation) and `/client/confirm-email/:hash` (email confirmation). Version 0.8.0 fixes the issue. Some workarounds are available. Configure a reverse proxy (e.g., Nginx, Apache, Cloudflare) to apply per-IP rate limiting to the `/client/reset-password-confirm/*` and `/staff/email/*` paths and/or use a WAF rule to limit request rates to these endpoints.

Scores

CVSS scores of CVE-2026-43926, by who scored it
Scored by	CVSS	Score	Vector
GitHub_MCNA (assigner)	4.0	Medium6.3	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
NVDNVD · Deferred	4.0	Medium6.3	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/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

EPSS (exploitation in 30 days): 0.22% · top 88% of all CVEs (7 Nov 2026)
CISA SSVC: Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.3.

Weakness

Affected products

FOSSBilling · FOSSBilling
- affected < 0.8.0

References (2)

https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-cqqm-p3x5-9fqg (opens in a new tab)x_refsource_CONFIRM
https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.0 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

[![CVE-2026-43926](https://trackcve.app/badge/CVE-2026-43926.svg)](https://trackcve.app/cve/CVE-2026-43926)

Record last updated 4 Jun 2026, 14:37 UTC.