According to the security researcher Hector Marco some versions of the Gmail app for Android are affected by a vulnerability (CVE-2015-1574) that can be exploited by attackers to cause the application to crash. In time I’m writing there no news regarding the presence of the flaw on other mobile OSs like iOS.
The expert explained that an attacker can remotely run a denial-of-service (DoS) attack against a user with a Gmail app for Android by sending him a specially crafted email. Any attempts to open the email again triggers a crash in the Gmail app.
“When the victim receives the malicious email, the application crashes while trying to download the email. Any attempt to open again the email application triggers a crash before the user can do anything. The email application can not be used until the offending email is removed,” Marco reported in a blog post.
The researcher successfully exploited the vulnerability on his Samsung Galaxy S4 Mini running version 4.2.2.0200 of Stock Android Email App, he explained that the bug appears to affect all older versions of the Stock Android Email App, though devices running 4.2.2.0400 and newer versions are not affected.
The effect of an attack can be really annoying for a user because the easiest way to restore a normal situation it to remove the malicious email from the Stock Android Email App. Consider also that this operation represents only a temporary solution because the attacker can send many malicious emails to the bitter end.
“Since the application crashes immediately, to remove the malicious email is a little bit tricky. The easiest and straightforward way to remove it is by using other email client (or via web) from the inbox at the email server. Another way is by disabling the internet connexion (Airplane mode) before launching the email reader, and then you can remove the offending email,” he added.
The expert explained that the flaw is caused by the incorrect handling of the Content-Disposition header, he discovered that to exploit the flaw it is sufficient to send an email with a malformed Content-Disposition header and cause the crash of the application.
The malformed header that doesn’t include parameters and cause the crash is:
Content-Disposition: attachment; filename=genome.jpeg;
as specified in the RFC2183
Email Android Google 4.2.2.0200 crasher ======================================= Author: Hector Marco <firstname.lastname@example.org> Website: http://hmarco.org $ ./crash_Android_Google_email_4.2.2.0200.py -s email@example.com -r firstname.lastname@example.org [+] Sending crafted message to: email@example.com [+] Malicious email successfully sent.
To fix the vulnerability in the affected Android Gmail app users can upgrade their email Android application to 4.2.2.0400 or higher. Unfortunately, the upgrade of the apps is not possible in all the Android versions. “The straightforward way to fix this issue is by updating the email Android application to 4.2.2.0400 or higher. Unfortunately this is not possible in all cases. For instance, current Samsung Galaxy 4 mini fully updated (17 Jan 2015) is vulnerable to this attack and not higher versions to 4.2.2.0200 are available after update the system from “Software updates”. Non-official Android ROMs or manually updates are possible but in some cases require root privileges in your device which in most cases causes a loss of warranty of the device. ” said Marco.