CVE-2026-63466

MEDIUMPre-NVD 4.14.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 92% of all CVEs by exploit prediction. 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
4.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 4.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Unleash is an open-source feature management platform. Prior to 8.0.3, FeatureEventFormatterMd.format in src/lib/addons/feature-event-formatter-md.ts assigns Mustache.escape to an identity function before rendering action and path templates. Because Mustache.escape is process-wide, the assignment disables escaping for subsequent Mustache.render calls in email-service.ts, webhook.ts, datadog.ts, and new-relic.ts. An editor-level user can place Slack or Microsoft Teams link syntax in an unrestricted username, trigger a feature event, and inject an attacker-labeled link into a trusted outbound notification channel, while other Mustache sinks remain unescaped until restart. This issue is fixed in version 8.0.3.

CVSS v3
4.1
EG Score
4.1(medium)
EG Risk
19(Track)
EG Risk 19/100SSVC: Track

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
Severity41% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
8%
KEV
Not listed

Published

August 21, 2026

Last Modified

September 9, 2026

Advisory Details (3)

Auto-updated Aug 21, 2026
Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

v8.0.3

Patch available: Unleash/unleash v8.0.3

https://github.com/Unleash/unleash/releases/tag/v8.0.3
github_commit Patch Available

commit 002012cfdbed (Unleash/unleash)

Patch available: Unleash/unleash v8.0.3 (contains commit 002012cfdbed)

https://github.com/Unleash/unleash/commit/002012cfdbedd2e9b7db9dc83b9f549f761db22e
github Patch Available

Global Mustache.escape override disables HTML escaping process-wide, enabling Slack/Teams link-injection via unrestricted username · Advisory · Unleash/unleash · GitHub

https://github.com/Unleash/unleash/security/advisories/GHSA-w4mq-xh27-6xpx

Vendor Advisories for CVE-2026-63466(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
unleash-server—8.0.3—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 48× 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. 2026-09-19 00:55 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-18 02:58 UTCEG score recompute
  4. 2026-09-17 05:03 UTCEG score recompute
  5. 2026-09-16 14:08 UTCEPSS rescore
  6. 2026-09-16 07:08 UTCEG score recompute
  7. 2026-09-16 05:15 UTCEPSS rescore
  8. 2026-09-15 09:13 UTCEG score recompute
  9. 2026-09-14 11:18 UTCEG score recompute
  10. 2026-09-12 15:28 UTCEG score recompute
  11. 2026-09-11 17:33 UTCEG score recompute
  12. 2026-09-11 14:53 UTCEPSS rescore
  13. 2026-09-11 09:37 UTCEPSS rescore
  14. 2026-09-10 19:36 UTCEG score recompute
  15. 2026-09-09 01:46 UTCEG score recompute
  16. 2026-09-08 22:01 UTCEPSS rescore
  17. 2026-09-07 16:01 UTCEPSS rescore
  18. 2026-09-07 11:03 UTCEG score recompute
  19. 2026-09-06 13:47 UTCEPSS rescore
  20. 2026-09-06 12:51 UTCEG score recompute
  21. 2026-09-05 15:31 UTCEPSS rescore
  22. 2026-09-04 17:00 UTCEG score recompute
  23. 2026-09-04 05:07 UTCEPSS rescore
  24. 2026-09-02 20:59 UTCEG score recompute
  25. 2026-09-02 14:12 UTCEPSS rescore
Show 23 more
  1. 2026-09-01 21:40 UTCEG score recompute
  2. 2026-09-01 13:54 UTCEPSS rescore
  3. 2026-09-01 04:40 UTCEPSS rescore
  4. 2026-08-31 01:50 UTCEG score recompute
  5. 2026-08-30 19:17 UTCEPSS rescore
  6. 2026-08-30 03:55 UTCEG score recompute
  7. 2026-08-30 01:22 UTCEPSS rescore
  8. 2026-08-29 06:00 UTCEG score recompute
  9. 2026-08-28 21:42 UTCEPSS rescore
  10. 2026-08-28 08:04 UTCEG score recompute
  11. 2026-08-27 14:25 UTCEPSS rescore
  12. 2026-08-27 10:04 UTCEG score recompute
  13. 2026-08-26 14:46 UTCEPSS rescore
  14. 2026-08-25 14:10 UTCEG score recompute
  15. 2026-08-25 13:49 UTCEPSS rescore
  16. 2026-08-24 16:12 UTCEG score recompute
  17. 2026-08-23 18:15 UTCEG score recompute
  18. 2026-08-23 00:19 UTCEPSS rescore
  19. 2026-08-21 22:25 UTCEG score recompute
  20. 2026-08-21 21:51 UTCEG score recompute
  21. 2026-08-21 19:22 UTCEG score recompute
  22. 2026-08-21 18:30 UTCEG score recompute
  23. 2026-08-21 18:29 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-63466?
CVE-2026-63466 is a medium vulnerability published on August 21, 2026. Unleash is an open-source feature management platform. Prior to 8.0.3, FeatureEventFormatterMd.format in src/lib/addons/feature-event-formatter-md.ts assigns Mustache.escape to an identity function before rendering action and path templates. Because Mustache.escape is process-wide, the assignment…
When was CVE-2026-63466 disclosed?
CVE-2026-63466 was first published in the National Vulnerability Database on August 21, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63466 actively exploited?
CVE-2026-63466 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 91.8% of all scored CVEs.
What is the CVSS score of CVE-2026-63466?
CVE-2026-63466 has a CVSS v3 base score of 4.1 (NVD).
How do I remediate CVE-2026-63466?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63466, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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