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

> Attackers can bypass rate limits on password reset endpoints to brute-force tokens, though high entropy mitigates practical success.

- **Severity:** Medium 6.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Jun 2026
- **Updated:** 4 Jun 2026
- **Also known as:** GHSA-cqqm-p3x5-9fqg

## What is CVE-2026-43926?

CVE-2026-43926 is a medium-severity missing authorization vulnerability in FOSSBilling, published on 4 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-307 (Improper Restriction of Excessive Authentication Attempts), CWE-204 (Observable Response Discrepancy)

## Which versions are affected by CVE-2026-43926?


## How do I fix CVE-2026-43926?

No fix has been published for CVE-2026-43926 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-43926 being exploited?

There is no known exploitation of CVE-2026-43926 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43926 and fix it if it is affected.

What it is: CVE-2026-43926 is a medium-severity missing authorization vulnerability in FOSSBilling, published on 4 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43926 in the wild and no public exploit code.

Affected product: FOSSBilling. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43926/ (Markdown: https://insights.sbomify.com/CVE-2026-43926/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43926
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43926
- OSV: https://osv.dev/vulnerability/CVE-2026-43926

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43926/
Summaries are generated and may contain mistakes; the official description above is the record.