# CVE-2026-53641 — FOSSBilling

> As of 2026-07-06, CVE-2026-53641 is a Medium-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in FOSSBilling, CVSS v4.0 4.8, EPSS 0.2% (20.4th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-53641 as of 2026-07-06; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-06

## What is CVE-2026-53641?

FOSSBilling is a free, open-source billing and client management system. Versions 0.6.0 through 0.7.2 have a stored cross-site scripting (XSS) vulnerability in the client-facing email history views of FOSSBilling. Email HTML content (`content_html`) is rendered into a JavaScript template literal using the `|raw` filter, bypassing all output escaping. An attacker with admin access can inject malicious JavaScript payloads into email content that execute in the browser of any client who views their email history. Version 0.8.0 contains a fix. Some workarounds are available. Restrict admin account access, audit email content in the database for suspicious payloads, and/or monitor client accounts for unusual activity.

The record classifies CVE-2026-53641 under weakness classes [CWE-79](https://intel.threadlinqs.com/cwe/CWE-79), [CWE-838](https://cwe.mitre.org/data/definitions/838.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:** 4.8 — Medium (derived from score) (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **EPSS (FIRST):** 0.2% probability of exploitation in the next 30 days, higher than 20.4% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-06

## Is CVE-2026-53641 being exploited?

It currently carries a trending score of 35 in the Threadlinqs vulnerability feed.

## Affected products and versions

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

## How to fix CVE-2026-53641

No vendor patch reference has been recorded for CVE-2026-53641 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-2026-53641

No threat campaign in the Threadlinqs corpus currently references CVE-2026-53641, 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 2026-07-08. 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-q6c8-6r72-35f7)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-53641
Full detection coverage and IOCs for threats exploiting CVE-2026-53641 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp