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: 0.3% (22nd 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
4.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 4.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
4.1MEDIUMmedium confidence
EG Risk
19
EG Risk 19/100CISA 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
Severity41% × 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
22nd
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

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
githubMentions a patch (unverified)

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 rangeFix by version rangeDependents
unleash-server—
  • every version up to 8.0.3: fixed in 8.0.3
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 46× 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. 2026-10-10 20:00 UTCEPSS rescore
  2. 2026-10-09 20:07 UTCEPSS rescore
  3. 2026-10-09 05:48 UTCEG score recompute
  4. 2026-10-08 17:13 UTCEPSS rescore
  5. 2026-10-08 04:55 UTCEG score recompute
  6. 2026-10-07 23:48 UTCEPSS rescore
  7. 2026-10-07 01:14 UTCEG score recompute
  8. 2026-10-06 15:18 UTCEPSS rescore
  9. 2026-10-06 03:04 UTCEG score recompute
  10. 2026-10-05 17:43 UTCEPSS rescore
  11. 2026-10-05 01:31 UTCEG score recompute
  12. 2026-10-04 23:22 UTCEPSS rescore
  13. 2026-10-04 02:30 UTCEG score recompute
  14. 2026-10-03 14:26 UTCEPSS rescore
  15. 2026-10-03 01:37 UTCEG score recompute
  16. 2026-10-02 17:56 UTCEPSS rescore
  17. 2026-10-02 03:42 UTCEG score recompute
  18. 2026-10-01 19:50 UTCEPSS rescore
  19. 2026-10-01 05:47 UTCEG score recompute
  20. 2026-09-30 15:03 UTCEPSS rescore
  21. 2026-09-30 07:52 UTCEG score recompute
  22. 2026-09-28 22:25 UTCEG score recompute
  23. 2026-09-28 13:51 UTCEPSS rescore
  24. 2026-09-28 00:23 UTCEG score recompute
  25. 2026-09-27 02:28 UTCEG score recompute
Show 56 more
  1. 2026-09-26 15:59 UTCEPSS rescore
  2. 2026-09-24 16:09 UTCEG score recompute
  3. 2026-09-23 18:14 UTCEG score recompute
  4. 2026-09-23 17:54 UTCEPSS rescore
  5. 2026-09-22 19:43 UTCEG score recompute
  6. 2026-09-20 20:45 UTCEG score recompute
  7. 2026-09-20 20:16 UTCEPSS rescore
  8. 2026-09-19 22:50 UTCEG score recompute
  9. 2026-09-19 00:55 UTCEG score recompute
  10. 2026-09-18 19:28 UTCEPSS rescore
  11. 2026-09-18 02:58 UTCEG score recompute
  12. 2026-09-17 05:03 UTCEG score recompute
  13. 2026-09-16 14:08 UTCEPSS rescore
  14. 2026-09-16 07:08 UTCEG score recompute
  15. 2026-09-16 05:15 UTCEPSS rescore
  16. 2026-09-15 09:13 UTCEG score recompute
  17. 2026-09-14 11:18 UTCEG score recompute
  18. 2026-09-12 15:28 UTCEG score recompute
  19. 2026-09-11 17:33 UTCEG score recompute
  20. 2026-09-11 14:53 UTCEPSS rescore
  21. 2026-09-11 09:37 UTCEPSS rescore
  22. 2026-09-10 19:36 UTCEG score recompute
  23. 2026-09-09 01:46 UTCEG score recompute
  24. 2026-09-08 22:01 UTCEPSS rescore
  25. 2026-09-07 16:01 UTCEPSS rescore
  26. 2026-09-07 11:03 UTCEG score recompute
  27. 2026-09-06 13:47 UTCEPSS rescore
  28. 2026-09-06 12:51 UTCEG score recompute
  29. 2026-09-05 15:31 UTCEPSS rescore
  30. 2026-09-04 17:00 UTCEG score recompute
  31. 2026-09-04 05:07 UTCEPSS rescore
  32. 2026-09-02 20:59 UTCEG score recompute
  33. 2026-09-02 14:12 UTCEPSS rescore
  34. 2026-09-01 21:40 UTCEG score recompute
  35. 2026-09-01 13:54 UTCEPSS rescore
  36. 2026-09-01 04:40 UTCEPSS rescore
  37. 2026-08-31 01:50 UTCEG score recompute
  38. 2026-08-30 19:17 UTCEPSS rescore
  39. 2026-08-30 03:55 UTCEG score recompute
  40. 2026-08-30 01:22 UTCEPSS rescore
  41. 2026-08-29 06:00 UTCEG score recompute
  42. 2026-08-28 21:42 UTCEPSS rescore
  43. 2026-08-28 08:04 UTCEG score recompute
  44. 2026-08-27 14:25 UTCEPSS rescore
  45. 2026-08-27 10:04 UTCEG score recompute
  46. 2026-08-26 14:46 UTCEPSS rescore
  47. 2026-08-25 14:10 UTCEG score recompute
  48. 2026-08-25 13:49 UTCEPSS rescore
  49. 2026-08-24 16:12 UTCEG score recompute
  50. 2026-08-23 18:15 UTCEG score recompute
  51. 2026-08-23 00:19 UTCEPSS rescore
  52. 2026-08-21 22:25 UTCEG score recompute
  53. 2026-08-21 21:51 UTCEG score recompute
  54. 2026-08-21 19:22 UTCEG score recompute
  55. 2026-08-21 18:30 UTCEG score recompute
  56. 2026-08-21 18:29 UTCMITRE cvelistV5first tracked

Related CVEs(same product + 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 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 0.3% probability of exploitation in the next 30 days (22nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63466?
CVE-2026-63466 has a CVSS base score of 4.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63466?
A fix for CVE-2026-63466 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-63466 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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