Feeds

Bind DNS resolver purged of critical DoS bug

Query domain, server goes boom

5 things you didn’t know about cloud backup

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. ®

Boost IT visibility and business value

More from The Register

next story
6 Obvious Reasons Why Facebook Will Ban This Article (Thank God)
Clampdown on clickbait ... and El Reg is OK with this
So, Apple won't sell cheap kit? Prepare the iOS garden wall WRECKING BALL
It can throw the low cost race if it looks to the cloud
EE accused of silencing customer gripes on social media pages
Hello. HELLO. Can EVERYTHING EVERYWHERE HEAR ME?!
Time Warner Cable customers SQUEAL as US network goes offline
A rude awakening: North Americans greeted with outage drama
Shoot-em-up: Sony Online Entertainment hit by 'large scale DDoS attack'
Games disrupted as firm struggles to control network
BT customers face broadband and landline price hikes
Poor punters won't be affected, telecoms giant claims
Broadband slow and expensive? Blame Telstra says CloudFlare
Won't peer, will gouge for Internet transit
prev story

Whitepapers

Best practices for enterprise data
Discussing how technology providers have innovated in order to solve new challenges, creating a new framework for enterprise data.
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.
Advanced data protection for your virtualized environments
Find a natural fit for optimizing protection for the often resource-constrained data protection process found in virtual environments.
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.
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?