Vulnerability

Ypsomed mylife App and Cloud encrypted traffic with hard-coded secrets and fixed IVs

MedDevice Cyber Staff · Jul 15 · 3 min read · Via CISA ICSMA-21-196-01

CISA published advisory ICSMA-21-196-01 on July 15, 2021, covering four vulnerabilities in the Ypsomed mylife App, versions before 1.7.5, and the mylife Cloud, versions before 1.7.2. Julian Suleder, Linda Huischen and Nils Emmerich of ERNW Research and Dr. Oliver Matula of ERNW reported them to Germany's BSI under the ManiMed project on manipulation of medical devices.

Two flaws sit in the cloud login flow. The mylife Cloud discloses password hashes during registration (CVE-2021-27491, CVSS v3 5.8). It also reflects the user's password during login after redirecting from an HTTPS endpoint to an HTTP one (CVE-2021-27495, CVSS 6.3, the highest in the set).

The other two concern the app's own encryption layer on top of the transport. It uses non-random IVs (CVE-2021-27499) and derives its protection from hard-coded secrets (CVE-2021-27503), both CVSS 5.4. Either lets a man-in-the-middle tamper with messages.

Ypsomed updated the mylife Cloud backend to fix the server-side issues and recommends users update the app to 1.7.5 or later.

Custom encryption layered over TLS adds code and risk, and here it was built on the two most common crypto mistakes.

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Remediation Desk

For ProvidersOperators, hospitals, and clinical engineering

Ypsomed fixed the mylife Cloud backend; users should update the mylife App to 1.7.5 or later. Anyone who registered or logged in on an affected version should change their mylife password, since hashes and passwords could be exposed.

Update the mylife App. Install version 1.7.5 or later on every phone.
Change mylife passwords. Reset passwords used on affected app or cloud versions.
Avoid untrusted networks. The tampering flaws need a man-in-the-middle position, so skip public Wi-Fi until updated.

For Device ManufacturersAm I affected, and how to fix the class

Am I affected?

This class applies to devices with the signals and properties below. Check them against your product to gauge exposure. The named product rows list what the sources state about the affected product.

Required

Cloud connectivity Mobile app

Contributing

User accounts Home use Therapy delivery

mylife App

PID-4113 Mobile app

mylife Cloud

PID-3321 Cloud connectivity User accounts

Fix the class in your product

Passwords are reversible or one key is shared across every install. As the maker, hash credentials with a purpose-built password algorithm, derive keys uniquely per installation, and bind tokens so a captured one cannot be replayed.

Hash, do not encode. Store credentials with a salted, memory-hard algorithm (argon2id or scrypt).
Derive keys per install. Never compile a shared key into the image; back it with a secure element.
Bind tokens against replay. Tie tokens to expiry, a nonce, and session context.

Mapped EMB3D mitigations

Questions & Answers

What is CVE-2021-27503 in the Ypsomed mylife App?

CVE-2021-27503 (CVSS v3 5.4) means the Ypsomed mylife App before 1.7.5 encrypts credentials on the application layer of its protocol with mylife Cloud using hard-coded secrets, letting man-in-the-middle attackers tamper with messages. CISA published it in ICSMA-21-196-01 on July 15, 2021.

Do mylife Cloud users need to do anything about ICSMA-21-196-01?

Ypsomed updated the mylife Cloud backend to fix the cloud issues in versions before 1.7.2. Users should update the mylife App to version 1.7.5 or later, according to CISA advisory ICSMA-21-196-01 from July 15, 2021.

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Key Facts

Product 1: mylife App before 1.7.5 (Ypsomed)
Device Type: Diabetes management mobile app
Product 2: mylife Cloud before 1.7.2 (Ypsomed)
Device Type: Diabetes data cloud service
Materials: mylife App < 1.7.5, fixed in 1.7.5; mylife Cloud < 1.7.2, fixed in 1.7.2
Components: Mobile Application, Cloud Service
Interfaces: TLS, TCP
Dataflows: mylife App to mylife Cloud with application-layer encrypted messages; User to mylife Cloud login with password reflected after HTTPS-to-HTTP redirect; mylife Cloud to User registration response disclosing password hashes
Assets: user password hashes (Credentials); user login password (Credentials); hard-coded secrets for application-layer encryption (Symmetric Encryption Keys)
Advisory: ICSMA-21-196-01
CVEs: CVE-2021-27491, CVE-2021-27503
Severity: Medium
Disclosed: Jul 15, 2021
Source: CISA ICSMA-21-196-01

Sources

Ypsomed: on the record

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