# CVE-2026-55666: Rocket.Chat: Email Parameter Fallback Leads To Account Takeover Within Apple OAuth

> Attackers can take over accounts by forging Apple OAuth tokens that omit the email field, causing the application to accept an attacker-supplied email address.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Jun 2026
- **Updated:** 29 Jun 2026
- **Also known as:** GHSA-wx3c-76rf-wpwf

## What is CVE-2026-55666?

CVE-2026-55666 is a critical authentication bypass vulnerability in RocketChat Rocket.Chat, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-288 (Authentication Bypass Using an Alternate Path or Channel), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-55666?


## How do I fix CVE-2026-55666?

No fix has been published for CVE-2026-55666 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-55666 being exploited?

There is no known exploitation of CVE-2026-55666 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55666 and fix it if it is affected.

What it is: CVE-2026-55666 is a critical authentication bypass vulnerability in RocketChat Rocket.Chat, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-55666 in the wild and no public exploit code.

Affected product: RocketChat Rocket.Chat. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55666/ (Markdown: https://insights.sbomify.com/CVE-2026-55666/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55666
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55666
- OSV: https://osv.dev/vulnerability/CVE-2026-55666

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55666/
Summaries are generated and may contain mistakes; the official description above is the record.