Feeds

Weaponised Flash flaw can pinch just about anything from anywhere

This is a 'patch now or regret it sooner-rather-than-later' mess for you and webmasters

Choosing a cloud hosting partner with confidence

Get cracking with the latest Flash upgrade, because the vulnerability it patches is a peach, allowing a cross-site request forgery (CSRF) attack for stealing user credentials.

According to the Switzerland-based Google engineer that turned up the vulnerability, Michele Spagnuolo, sites that are/were vulnerable to the attack included various Google domains, YouTube, Twitter, Instagram, Tumblr and eBay.

“I present Rosetta Flash, a tool for converting any SWF file to one composed of only alphanumeric characters in order to abuse JSONP endpoints, making a victim perform arbitrary requests to the domain with the vulnerable endpoint and exfiltrate potentially sensitive data, not limited to JSONP responses, to an attacker-controlled site,” Spagnuolo writes.

Rosetta Flash takes a combination of three characteristics of Flash and JSONP which he says were all “well known” but ignored, since nobody had previously worked out how to combine them into an attack.

Rosetta Flash diagram

Rosetta Flash creates alphanumeric-only SWFs that can be used to embed a JSONP CSRF attack.

Image: Michale Spagnuolo

The first component of the attack is that a SWF file can perform cookie-carrying GET and POST requests to the domain that hosts it, with no cross-domain checks. As a result, Spagnuolo writes, a site that lets attackers upload SWF files on a sensitive domain “can make the victim perform requests that have side effects and exfiltrate sensitive data to an external, attacker-controlled, domain”.

The second part of the attack uses JSONP: this, he writes, “allows an attacker to control the first bytes of the output of an endpoint by specifying the callback parameter in the request URL”. JSONP is usually restricted to alphabetic characters only – and this is where Spagnuolo's Rosetta Flash tool turns the SWF/JSONP combo into an attack.

The third part is that an SWF file (with a content type-forcing tag) will be executed if it looks like a valid Flash file – so a modified malicious file on an attacker's domain can be the vector.

Rosetta Flash (at github) is the key tool in all of this: it takes the binary data in an SWF, and maps all the non-alphabetic bytes to the alphabet. That means a malicious SWF will be recognised and executed (the full details of his brute-forcing techniques are described in detail at his blog post).

In the proof-of-concept, Spagnuolo demonstrates how to get parameters passed as FlashVars to perform a GET request with the victim's cookie, and POST a variable with the exfiltrated data.

For those whose browsers don't auto-update, Adobe has pushed a Flash update here, and Google (which he notified privately) has fixed its domains. According to Ars, Tumblr has been patched.

As well as the blog post, Spagnuolo has published a slide set here. ®

Beginner's guide to SSL certificates

More from The Register

next story
NASTY SSL 3.0 vuln to be revealed soon – sources (Update: It's POODLE)
So nasty no one's even whispering until patch is out
Russian hackers exploit 'Sandworm' bug 'to spy on NATO, EU PCs'
Fix imminent from Microsoft for Vista, Server 2008, other stuff
US government fines Intel's Wind River over crypto exports
New emphasis on encryption as a weapon?
To Russia With Love: Snowden's pole-dancer girlfriend is living with him in Moscow
While the NSA is tapping your PC, he's tapping ... nevermind
Forget passwords, let's use SELFIES, says Obama's cyber tsar
Michael Daniel wants to kill passwords dead
Slap for SnapChat web app in SNAP mishap: '200,000' snaps sapped
This is what happens if you hand your username and password to a 3rd-party
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Win a year’s supply of chocolate
There is no techie angle to this competition so we're not going to pretend there is, but everyone loves chocolate so who cares.
Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.