CVE-2026-55666

CRITICALPre-NVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 79% 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
9.3
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.3Exploit: NoneExposed: 0

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

Rocket.Chat is an open-source, secure, fully customizable communications platform. Prior to 8.5.1, 8.4.4, 8.3.6, 8.2.6, 8.1.6, 8.0.7, and 7.10.13, in apps/meteor/app/apple/server/loginHandler.ts, handleIdentityToken parses a JWT issued by Apple during the OAuth flow. The try block checks for an email parameter. If the JWT does not contain an email address, the application falls back to accepting an arbitrary email value supplied directly in the request. Attackers are able to forge Apple JWTs that do not contain an email address and leverage this vulnerability to carry out account takeover attacks. This vulnerability is fixed in 8.5.1, 8.4.4, 8.3.6, 8.2.6, 8.1.6, 8.0.7, and 7.10.13.

CVSS v3
9.3
EG Score
9.3(medium)
EPSS
21.4%
KEV
Not listed

Published

June 24, 2026

Last Modified

June 29, 2026

Advisory Details (1)

Auto-updated Jun 25, 2026
Patch available. Sources: github.
github Patch Available

Email Parameter Fallback Leads To Account Takeover Within Apple OAuth · Advisory · RocketChat/Rocket.Chat · GitHub

https://github.com/RocketChat/Rocket.Chat/security/advisories/GHSA-wx3c-76rf-wpwf

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 56× in last 7d / 135× 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.

Showing the most recent 100 of 135 total refreshes for this CVE.

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  75. 2026-06-29 14:06 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-55666?
CVE-2026-55666 is a critical vulnerability published on June 24, 2026. Rocket.Chat is an open-source, secure, fully customizable communications platform. Prior to 8.5.1, 8.4.4, 8.3.6, 8.2.6, 8.1.6, 8.0.7, and 7.10.13, in apps/meteor/app/apple/server/loginHandler.ts, handleIdentityToken parses a JWT issued by Apple during the OAuth flow. The try block checks for an…
When was CVE-2026-55666 disclosed?
CVE-2026-55666 was first published in the National Vulnerability Database on June 24, 2026, with the most recent update on June 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55666 actively exploited?
CVE-2026-55666 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 21.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-55666?
CVE-2026-55666 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-55666?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55666, 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.

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