CVE-2026-54521

MEDIUMPre-NVD 6.16.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (23rd percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 6.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
6.1
EG Score
6.1MEDIUMmedium confidence
EG Risk
28
EG Risk 28/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity61% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
23rd
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 17, 2026

Last Modified

September 23, 2026

Advisory Details (3)

Auto-updated Sep 17, 2026
Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

1.2319 Elopteryx

Patch available: M66B/FairEmail 1.2319

https://github.com/M66B/FairEmail/releases/tag/1.2319
github_commit Patch Available

commit fb37bbfabf5e (M66B/FairEmail)

Patch available: M66B/FairEmail 1.2319 (contains commit fb37bbfabf5e)

https://github.com/M66B/FairEmail/commit/fb37bbfabf5e75d08f0cfa6ce9b84469d62a20a0
github Patch Available

Cross-site scripting (XSS) in AMP message rendering (ActivityAMP) · Advisory · M66B/FairEmail · GitHub

https://github.com/M66B/FairEmail/security/advisories/GHSA-r8ff-qr7g-pvw6

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 14× in last 7d / 35× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-04 23:42 UTCEG score recompute
  2. 2026-10-04 23:22 UTCEPSS rescore
  3. 2026-10-04 01:20 UTCEG score recompute
  4. 2026-10-03 14:26 UTCEPSS rescore
  5. 2026-10-03 02:56 UTCEG score recompute
  6. 2026-10-02 17:56 UTCEPSS rescore
  7. 2026-10-02 04:35 UTCEG score recompute
  8. 2026-10-01 19:50 UTCEPSS rescore
  9. 2026-10-01 05:52 UTCEG score recompute
  10. 2026-09-30 15:03 UTCEPSS rescore
  11. 2026-09-30 07:31 UTCEG score recompute
  12. 2026-09-29 15:22 UTCEPSS rescore
  13. 2026-09-29 09:09 UTCEG score recompute
  14. 2026-09-28 13:51 UTCEPSS rescore
  15. 2026-09-28 10:47 UTCEG score recompute
  16. 2026-09-27 13:48 UTCEPSS rescore
  17. 2026-09-27 12:26 UTCEG score recompute
  18. 2026-09-26 15:59 UTCEPSS rescore
  19. 2026-09-26 14:04 UTCEG score recompute
  20. 2026-09-24 16:50 UTCEG score recompute
  21. 2026-09-24 14:04 UTCEPSS rescore
  22. 2026-09-23 18:28 UTCEG score recompute
  23. 2026-09-23 17:54 UTCEPSS rescore
  24. 2026-09-23 12:21 UTCEG score recompute
  25. 2026-09-22 13:59 UTCEG score recompute
Show 10 more
  1. 2026-09-21 15:38 UTCEG score recompute
  2. 2026-09-20 20:16 UTCEPSS rescore
  3. 2026-09-19 18:55 UTCEG score recompute
  4. 2026-09-18 20:34 UTCEG score recompute
  5. 2026-09-18 20:10 UTCEG score recompute
  6. 2026-09-18 19:41 UTCEG score recompute
  7. 2026-09-18 19:28 UTCEPSS rescore
  8. 2026-09-17 21:20 UTCEG score recompute
  9. 2026-09-17 20:25 UTCEG score recompute
  10. 2026-09-17 20:24 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-54521?
CVE-2026-54521 is a medium vulnerability published on September 17, 2026. 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…
When was CVE-2026-54521 disclosed?
CVE-2026-54521 was first published on September 17, 2026, with the most recent update on September 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54521 actively exploited?
CVE-2026-54521 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (23rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-54521?
CVE-2026-54521 has a CVSS base score of 6.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-54521?
A fix for CVE-2026-54521 is available: update to the fixed version the vendor names in its advisory.

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