Feeds

MONSTER COOKIES can nom nom nom ALL THE BLOGS

Blog networks can be force-fed more than they can chew

Seven Steps to Software Security

Giant cookies could be used to create a denial of service (DoS) on blog networks, says infosec researcher Bogdan Calin.

Such an attack would work by feeding users cookies with header values so large that they trigger web server errors.

Calin created a proof of concept attack against the Google Blog Spot network after a customer reported problems with internal security testing. In his subsequent tests, he found that if one sends many cookies to a browser, sets them to never expire and includes pointers to a blog network's root domain, the user won't ever be able to see any blogs on the service.

Victims can tell if supersized cookies have been stuffed down their browser's throats when 400 errors such as "Your browser sent a request that this server could not understand. Size of a request header field exceeds server limit" appear.

Sydney security bod Wade Alcorn (@WadeAlcorn) said the attack would work if custom cookies could be set.

"This attack, denial-of-service by cookies, sets many long cookies, forcing the browser to create a very long request [that] is too long for the server to handle, and simply returns an error page," Alcorn said.

"The vulnerable browser won’t be able to visit that origin until the cookies are cleared.

"When a browser visits one of these [user-controlled] subdomains it will allow a cookie to be set on the parent domain [which] means that when a denial-of-service by cookies attack is launched, the victim browser will not be able to visit the parent domain or any of the subdomains."

For an application to be vulnerable it must provide an opportunity for the attacker to set custom cookies in the victim’s browser, Alcorn pointed out.

Chrome users were not affected when perusing Blog Spot but were on other unnamed domains.

Alcorn said a Google security rep told him the risk was a problem for web browser developers to fix, rather than a lone web app providers, and welcomed ideas that could squash the vector. ®

Mobile application security vulnerability report

More from The Register

next story
Yorkshire cops fail to grasp principle behind BT Fon Wi-Fi network
'Prevent people that are passing by to hook up to your network', pleads plod
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
NEW, SINISTER web tracking tech fingerprints your computer by making it draw
Have you been on YouPorn lately, perhaps? White House website?
LibreSSL RNG bug fix: What's all the forking fuss about, ask devs
Blow to bit-spitter 'tis but a flesh wound, claim team
Attackers raid SWISS BANKS with DNS and malware bombs
'Retefe' trojan uses clever spin on old attacks to grant total control of bank accounts
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
Don't look, Snowden: Security biz chases Tails with zero-day flaws alert
Exodus vows not to sell secrets of whistleblower's favorite OS
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Reducing security risks from open source software
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.