Google AOSP Email App HTML Injection

1. Vulnerability Properties

Title: Google AOSP Email App HTML Injection
CVE ID: Pending
CVSSv3 Base Score: 6.3 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L)
Vendor: Google
Products: AOSP Email App
Advisory Release Date:  16 November 2015
Advisory URL: https://labs.integrity.pt/advisories/google-aosp-email-app-html-injection/
Credits: Discovery by Cláudio André <ca[at]integrity.pt>

2. Vulnerability Summary

A remote attacker is able to send a crafted email with a payload that redirects the user to a target url as soon as he opens the email.

3. Technical Details

The vulnerability can be confirmed by sending a HTML email with the following content:

<meta http-equiv=”refresh” content=”0;URL=’http://www.maliciousurl.com’” />

Exploiting this vulnerability could allow an attacker to redirect a user to a malicious website, allowing hooking the browser with malicious JavaScript, launching phishing attacks, explore intent-based URI or browser vulnerabilities.

4. Vulnerable Versions

• Confirmed on versions up until 7.0.

5. Solution

• Users from Android Ice Cream Sandwich (4.0.3) upwards, should migrate the accounts from the AOSP Email App to the Gmail App, since the Gmail App version 5.0+ is supported.
• Users with previous Android versions should upgrade to Ice Cream Sandwich or above where possible or use a different email client.

6. Vulnerability timeline

• 16/6/2015 : Issue reported to Google.
• 26/6/2015 : Issue 178228 created for this vulnerability.
• 7/7/2015: Asked for feedback.
• 4/8/2015: Google replied: After investigation we re-classified this issue as Low severity due to the limited risk. The email app in KitKat doesn't execute Javascript, so the potential for exploitation is low.Because it's a low severity, we have no plans to backport the fix to KitKat per our backport policy posted in the "Notifying Partners" section of https://source.android.com/devices/tech/security/overview/updates-resources.html. The issue doesn't apply to later versions of Android.
• 4/8/2015: We replied that this issue was not regarding Javascript but HTML, and that this issue has big potential for phishing attacks. (We did not find any version where Javascript execution was possible)
• 24/8/2015: Asked for feedback.
• 22/9/2015: Asked for feedback.
• 23/10/2015: Google replied that there´s currently no plan to fix this issue.
• 16/11/2015: Advisory released