Feeds

Proxy server bug exposes websites' private parts

By the dozen

  • alert
  • submit to reddit

SANS - Survey on application security programs

Updated Computer networks that use proxy servers to automatically redirect browser connections should be on the lookout for a serious architectural flaw that could allow attackers to remotely access intranets and other website resources that are normally off limits, security experts are warning.

At least four proxy server vendors, including QBIK New Zealand, SmoothWall, Squid and Ziproxy remain vulnerable to flaw, according to this advisory from the US Computer Emergency Readiness Team. Products from several dozen additional vendors were vulnerable but have been updated in the past few weeks. Network administrators will need to install the latest versions to ensure their networks aren't vulnerable.

The architectural flaw affects proxy servers that run in what's known as transparent interception mode. The configuration allows servers to intercept and redirect network connections without any user interaction or special browser settings. To exploit the bug, attackers can manipulate host header values using active content such as Java and Flash.

"An attacker may be able to make full connections to any website or resource that the proxy can connect to," CERT warns. "These sites may include internal resources such as intranet sites that would not usually be exposed to the internet."

The vulnerability was originally reported by Robert Auger of PayPal's Information Risk Management team. In a note posted on Cgisecurity.com, he said he planned to release a more detailed technical analysis in March, presumably after network administrators have had a chance to patch vulnerable networks. Based on the bare-bones analysis provided by CERT, it appears the bug may also threaten end users, presumably through phishing attacks.

"To successfully exploit this issue, an attacker would need to either convince a user to visit a web page with malicious active content or be able to load the active content in an otherwise trusted site," the advisory reads.

The good news is that the vulnerability only seems to affect proxy servers running in transparent mode. Browser same-origin policies, which prevent cookies and other types of content set by one domain from being accessed or manipulated by a different address, make it hard for attackers to reuse authentication credentials to gain unauthorized access.

CERT is encouraging admins to update their proxy servers and in the meantime to follow a series of workarounds.

It remains unclear how common transparent interception is used in proxy servers. While several security experts said few large companies use it, Kevin Johnson, a senior security analyst at InGuardians, said the configuration is often used when implementing reverse proxies for load balancing, content caching and other network management services.

"It's a good thing this was announced," he told The Register. "Proxy servers have been a point of interest for the last decade." ®

High performance access to file storage

More from The Register

next story
Obama allows NSA to exploit 0-days: report
If the spooks say they need it, they get it
Putin tells Snowden: Russia conducts no US-style mass surveillance
Gov't is too broke for that, Russian prez says
Snowden-inspired crypto-email service Lavaboom launches
German service pays tribute to Lavabit
Mounties always get their man: Heartbleed 'hacker', 19, CUFFED
Canadian teen accused of raiding tax computers using OpenSSL bug
Heartbleed exploit, inoculation, both released
File under 'this is going to hurt you more than it hurts me'
Arts and crafts store Michaels says 3 million credit cards exposed in breach
Meanwhile, Target investigators prepare for long process in nabbing hackers
Canadian taxman says hundreds pierced by Heartbleed SSL skewer
900 social insurance numbers nicked, says revenue watchman
prev story

Whitepapers

SANS - Survey on application security programs
In this whitepaper learn about the state of application security programs and practices of 488 surveyed respondents, and discover how mature and effective these programs are.
Combat fraud and increase customer satisfaction
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Top three mobile application threats
Learn about three of the top mobile application security threats facing businesses today and recommendations on how to mitigate the risk.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.