# CVE-2026-53646 — FOSSBilling

> As of 2026-07-07, CVE-2026-53646 is a High-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in FOSSBilling, CVSS v4.0 7.7, EPSS 0.2% (11.8th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-53646 as of 2026-07-07; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-07

## What is CVE-2026-53646?

FOSSBilling is a free, open-source billing and client management system. In versions 0.5.6 through 0.7.2, when a `ClientPasswordReset` record already exists for a client (from a previous unexpired reset request), subsequent calls to the `reset_password` guest API endpoint reuse the existing token instead of generating a new one. The 15-minute validity window is anchored to the first request's `created_at` timestamp, not the time of the most recent email. An attacker who obtained the original reset link remains able to use it even after the victim requests a new reset, because the original token is never invalidated or rotated. Version 0.8.0 patches 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` endpoint to minimize the window of opportunity, and/or manually clear expired `client_password_reset` records from the database after a client reports a suspected compromise.

The record classifies CVE-2026-53646 under weakness class [CWE-640](https://cwe.mitre.org/data/definitions/640.html). 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 91 days ago.

## Severity and exploitation probability

- **CVSS v4.0 base score:** 7.7 — High (derived from score) (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.2% probability of exploitation in the next 30 days, higher than 11.8% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-06, last modified 2026-07-07

## Is CVE-2026-53646 being exploited?

It currently carries a trending score of 33 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [FOSSBilling](https://intel.threadlinqs.com/vendors/fossbilling): FOSSBilling

## How to fix CVE-2026-53646

No vendor patch reference has been recorded for CVE-2026-53646 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-53646

No threat campaign in the Threadlinqs corpus currently references CVE-2026-53646, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-07-07. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-vp66-w6rc-x32p)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-53646
Full detection coverage and IOCs for threats exploiting CVE-2026-53646 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp