Feeds

Bind DNS resolver purged of critical DoS bug

Query domain, server goes boom

Build a business case: developing custom apps

Makers of the internet's most widely used domain name resolution software have patched a vulnerability that allowed attackers to crash many systems that run the program.

By querying a domain with large resource record sets (or RRsets) and trying to negatively cache a response, attackers can cause the Bind server to crash. The denial-of-service vulnerability threatens systems that use various versions of Bind 9 as a caching resolver. DNS systems use negative caching to improve resolution response time by preventing servers from looking up non-existent domains over and over.

“In this vulnerability, very large RRSIG RRsets included in a negative response can trigger an assertion failure that will crash named (Bind 9 DNS) due to an off-by-one error in a buffer size check,” read an advisory published by the Internet Systems Consortium, the group that maintains Bind.

The advisory continued:

The nature of this vulnerability would allow remote exploit. An attacker can set up a DNSSEC signed authoritative DNS server with large RRSIG RRsets to act as the trigger. The attacker would then find ways to query an organization’s caching resolvers for non-existent names in the domain served by the bad server, getting a response that would “trigger” the vulnerability. The attacker would require access to an organization’s caching resolvers; access to the resolvers can be direct (open resolvers), through malware (using a BOTNET to query negative caches), or through driving DNS resolution (a SPAM run that has a domain in the E-mail that will cause the client to perform a lookup).

The advisory urges users to upgrade to Bind 9.4-ESV-R4-P1, 9.6-ESV-R4-P1, 9.7.3-P1, or 9.8.0-P2, which are available here.

As a partial workaround, users can restrict the DNS caching resolver system.

“Active exploitation can be accomplished through malware or Spam/Malvertizing actions that will force authorized clients to look up domains that would trigger this vulnerability,” the advisory warns. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
UK fuzz want PINCODES on ALL mobile phones
Met Police calls for mandatory passwords on all new mobes
Canadian ISP Shaw falls over with 'routing' sickness
How sure are you of cloud computing now?
Don't call it throttling: Ericsson 'priority' tech gives users their own slice of spectrum
Actually it's a nifty trick - at least you'll pay for what you get
Three floats Jolla in Hong Kong: Says Sailfish is '3rd option'
Network throws hat into ring with Linux-powered handsets
Fifteen zero days found in hacker router comp romp
Four routers rooted in SOHOpelessly Broken challenge
New Sprint CEO says he will lower axe on staff – but prices come first
'Very disruptive' new rates to be revealed next week
PwC says US biz lagging in Internet of Things
Grass is greener in Asia, say the sensors
Ofcom sees RISE OF THE MACHINE-to-machine cell comms
Study spots 9% growth in IoT m2m mobile data connections
O2 vs Vodafone: Mobe firms grab for GCHQ, gov.uk security badge
No, the spooks love US best, say rival firms
Ancient pager tech SMS: It works, it's fab, but wow, get a load of that incoming SPAM
Networks' main issue: they don't know how it works, says expert
prev story

Whitepapers

Endpoint data privacy in the cloud is easier than you think
Innovations in encryption and storage resolve issues of data privacy and key requirements for companies to look for in a solution.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Top 8 considerations to enable and simplify mobility
In this whitepaper learn how to successfully add mobile capabilities simply and cost effectively.
Solving today's distributed Big Data backup challenges
Enable IT efficiency and allow a firm to access and reuse corporate information for competitive advantage, ultimately changing business outcomes.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.