Facebook recently patched a vulnerability in WhatsApp for Android that may have allowed hackers to execute arbitrary code and gain access to sensitive user data by sending specially crafted GIF files.
The security hole, discovered by a researcher who uses the online moniker Awakened, has been described as a double-free bug and it has been assigned the CVE identifier CVE-2019-11932.
The vulnerability was reported by the researcher to Facebook and it was patched with the release of version 2.19.244. The flaw allows remote code execution on devices running Android 8.1 and 9.0, but on previous versions of the mobile operating system it can only be exploited for denial-of-service (DoS) attacks, Awakened said.
The vulnerability exists in an open source library named libpl_droidsonroids_gif.so, which is used by WhatsApp to generate previews of GIF files. The bug has also been fixed in libpl_droidsonroids_gif.so.
Exploiting the vulnerability can allow a malicious actor to escalate privileges on a compromised Android phone and gain access to files stored on the device, including the WhatsApp messages database. It can also be used to create a remote shell in the context of WhatsApp.
Exploitation involves sending a malicious GIF file, which automatically triggers the vulnerability when the targeted user opens the WhatsApp Gallery; for example, when they want to send a picture to one of their contacts.
However, exploitation is not as straightforward as it may seem. The attacker needs to be in the victim’s contact list for the malicious GIF file to be automatically downloaded to the targeted device. Moreover, remote code execution can only be achieved if CVE-2019-11932
is combined with another vulnerability or with a malicious app that is already present on the target device.
“[The] vulnerability shows how software can misbehave when presented with unexpected or malformed input. The memory allocator showed peculiar, exploitable behavior when asked to allocate 0 bytes of memory. Negative testing and fuzz testing during development of the memory allocator could have surfaced this behavior, allowing it to be fixed well ahead of release,” Jonathan Knudsen, senior security strategist at Synopsys, told SecurityWeek.
Knudsen added, “This is not a vulnerability where an attacker can send a special GIF and take over your phone. An attacker would first need to exploit another vulnerability on your phone to gain insight into the memory layout; only then could a crafted GIF be sent that would result in system compromise, and even then, you would need to open the WhatsApp gallery before the exploit would be triggered.”
Technical details, proof-of-concept (PoC) code, and a video demonstrating the exploit in action have been made available by Awakened.
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