sb-as logo
Story image

Bug makes Android phones hackable via PNG image files

08 Feb 2019

Article by Deep Secure CTO Dr Simon Wiseman

Google has recently announced a security flaw in the way Android devices handle PNG images. Apparently, it’s a heap overflow in the SkPngCodec.

This means any application handling PNG files that have been carefully crafted by an attacker can end up running the attacker’s code.

This means a web browser can fetch a crafted image from a web site and the attacker now is in control of the browser and its environment.

That means it has access to your stored passwords and you’ve given away access to all the secure sites you visit.

The same goes for your email client – the attacker has control of your mailbox so can intercept your mail, perfect for harvesting password resets, and generate mail on your behalf, ideal for propagating the attack within your organisation.

But Google is responsible, and the announcement was held back until a fix was in place.

However, patches to phones are rolled out slowly.

That means today is the zero-day for this attack and it’s going to be weeks until it is defeated. It’s a bad place for such a vulnerability to turn up.

How could this happen?

The PNG file format is well-defined – it’s one of the best specifications around for this type of attack.

The basic structure of a PNG is simple, and it’s hard to see how a mistake like this could be made handling it (not like GIF which suffered in the past from a buffer overflow due to its slightly crazy structure).

The compression algorithm used is well understood and well used.

But there are some complex parts to the format, in particular, the way it handles interleaved scanlines.

It’s not impossible to imagine the library making a mistake here, when it tries to reorder the scan lines into display order it has some tricky calculations to do to fill the buffer correctly.

And PNGs can contain ancillary data, such as colour profiles, which are very complex structures that, if malformed, might be mishandled.

These sort of mistakes are very hard to find through testing because it’s not really possible to anticipate all the ways things could go wrong and there are too many possibilities to systematically check them all.

What can the average user do right now?

First off make sure you take all the updates available and keep doing this daily for the next few weeks.

Second, tell your mobile browser to forget all the passwords it holds.

What’s to be done once the panic is over?

Most will relax and be thankful that the problem has been found and fixed.

But anyone concerned with defending systems against cyber attack will be wanting to know if anything could have been done to defend against the attack before it was known about, and what can be done to defend against the next one of this kind.

What’s clear is that trying to detect problems like this does not work.

They cannot be anticipated so you don’t know what to look for.

The attacker will always be able to evade any attempts to detect their attack.

Story image
How Bitcoin could impact the cyber-threat landscape
Bitcoin's escalating valuation has made some criminal organisations and malicious individuals very wealthy. The impact of this growth in wealth may have a severe impact on the future threat landscape.More
Story image
Google Cloud announces availability of zero trust platform BeyondCorp Enterprise
The platform directly replaces BeyondCorp Remote Access, which was brought to the market in April 2020 as Google’s first foray into the zero trust space.More
Story image
Malware vendors look to marketing to spread Android RAT
What happens when an Android malware vendor teams up with a marketer? It turns out the answer is quite a lot.More
Story image
IronNet expands Asia Pacific presence with new strategic partnership
“The combination of M.Tech’s extensive network in Asia Pacific and our unparalleled expertise in threat intelligence and detection will help more enterprises across the region to proactively identify and take down known and unknown threats before they happen.”More
Story image
Kaspersky steps in to protect automotive industry from cyber threats
The company’s TI report, previously available for a selected range of customers, is able to provide car manufacturers with in-depth analysis of industry-specific security threats.More
Story image
Trend Micro adds cloud-native container security to Cloud One Services Platform
Designed to ease the security of container builds, deployments and runtime workflows, the new service helps developers accelerate innovation and minimise application downtime across Kubernetes environments.More