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.
CVE-2026-63466
MEDIUMPre-NVD 4.14.1
EchelonGraph scoreLOW confidence
This medium-severity CVE scores 4.1 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: cna:github_m
4.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 4.1Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 4.1
- EG Score
- 4.1(low)
- EG Risk
- 18(Track)EG Risk 18/100SSVC: 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 computedSeverity41% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- —
- EPSS %ILE
- —
- KEV
- Not listed
Published
August 21, 2026
Last Modified
August 21, 2026
Advisory Details (3)
Auto-updated Aug 21, 2026Patch 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/v8.0.3github_commit Patch Available
commit 002012cfdbed (Unleash/unleash)
Patch available: Unleash/unleash v8.0.3 (contains commit 002012cfdbed)
https://github.com/Unleash/unleash/commit/002012cfdbedd2e9b7db9dc83b9f549f761db22egithub 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-xh27-6xpxVendor 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.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 4× in last 7d / 4× 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.
- 2026-08-21 21:51 UTCEG score recompute
- 2026-08-21 19:22 UTCEG score recompute
- 2026-08-21 18:30 UTCEG score recompute
- 2026-08-21 18:29 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-116
Frequently asked(4)
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. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-63466?
CVE-2026-63466 has a CVSS v4.0 base score of 4.1 (CNA self-assessment; NVD's own analysis pending). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
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
Explore the affected products and dependency analysis for CVE-2026-63466
Is Your Infrastructure Affected by CVE-2026-63466?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.