IE 7 bug reopens debate over patch responsibilities

Researchers argue over who to blame; Microsoft again denies there's a bug

Security researchers are again arguing over who is responsible -- Microsoft or third-party developers -- for protocol-handling bugs after a researcher said late last week that Internet Explorer 7 can be used to trick users into launching malware.

Posting to the Full Disclosure mailing list, Juergen Schmidt, a researcher at Heise Security, blamed IE 7 for passing invalid Uniform Resource Identifiers (URI) to Windows XP. Specifically, said Schmidt, IE 7 accepts URLs from other applications that include the "%" [percent] character, which can launch software or scripts on users' machines if they click on a malformed link.

According to Schmidt and others, the earlier IE 6 doesn't have the bug, indicating that something broke between versions. "Post-IE7 has a flaw/threat/vulnerability it hasn't had pre-IE7," said Thierry Zoller, a penetration tester at German security firm n.runs.

Windows' URI protocol handling, the technology that lets browsers run other programs via commands in the URL, has been criticized since July, when Norwegian researcher Thor Larholm demonstrated how IE and rival Firefox could be used to run malicious code. Even then, researchers feuded over responsibility. Mozilla patched Firefox several days later, but Microsoft declined to fix IE, saying that it didn't consider the issue a vulnerability in its software.

Schmidt identified several applications, including Adobe System's Acrobat Reader, the Netscape browser and Miranda, an IM client, that he said improperly handle URIs with the percent symbol, and he hinted that there were plenty more.

His post drew reaction on Full Disclosure. "The applications are accepting arbitrary input and not validating correctly," said Roger Grimes, a security consultant who said he works at Microsoft. "How is that a Microsoft or Windows problem? How could Microsoft determine ahead of time what is and isn't [a] legitimate character to pass to applications they don't own?"

"How is that _not_ a Windows Problem?" replied Zoller. "It's not that they should decide what to pass or not to pass on, the problem in the example Juergen sent is [that] they pass internally, not to third-party applications."

"If the application is what exposes the URI-handling routine to untrusted code from the Internet, then it's the application's job to make sure that code is trusted before exposing system components to its commands, no?" asked another user who went by the name "Geo."

Microsoft denied responsibility for any vulnerability in July and repeated that to Schmidt after he asked if the company's security center would address the problem. "After its thorough investigation, Microsoft has revealed that this is not a vulnerability in a Microsoft product." The company was not available early this week to confirm that its previous comment remains its official position.

Last summer, however, an IE program manager said it would be "very difficult" to retroactively add checks for possibly invalid URIs and, citing the "limitless variety of applications and their unique capabilities," pointed to the those applications as the real source of the problem. "It is the responsibility of the receiving (called) application to make sure it can safely process the incoming parameters," said Markellos Diorinos.

Some security researchers don't see it the same way. For example, Symantec issued an alert to customers of its DeepSight threat system, warning them of the bug and putting the onus on Microsoft. "This issue is due to a flaw in Microsoft Windows when it attempts to determine which application should be utilized when interpreting protocol-handlers such as 'mailto:', 'http:', and others," the alert read.

"The fundamental flaw here is that Windows' built-in URI handler doesn't invoke external programs correctly, resulting in a shell-injection attack," argued Glynn Clements on the Full Disclosure thread begun by Schmidt. "Modifying individual programs to protect against a shell-injection bug in Windows' URI handler is a work-around, not a fix."

According to a notice it gave last week, Microsoft will patch Internet Explorer tomorrow to fix what it has described as a "critical" vulnerability. Although the expected security update will include changes to IE 7, Microsoft does not specify the vulnerabilities it will address before it posts its patches.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Gregg Keizer

Computerworld
Show Comments

Cool Tech

SanDisk MicroSDXC™ for Nintendo® Switch™

Learn more >

Breitling Superocean Heritage Chronographe 44

Learn more >

Toys for Boys

Family Friendly

Panasonic 4K UHD Blu-Ray Player and Full HD Recorder with Netflix - UBT1GL-K

Learn more >

Stocking Stuffer

Razer DeathAdder Expert Ergonomic Gaming Mouse

Learn more >

Christmas Gift Guide

Click for more ›

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

George Khoury

Sharp PN-40TC1 Huddle Board

The biggest perks for me would be that it comes with easy to use and comprehensive programs that make the collaboration process a whole lot more intuitive and organic

David Coyle

Brother PocketJet PJ-773 A4 Portable Thermal Printer

I rate the printer as a 5 out of 5 stars as it has been able to fit seamlessly into my busy and mobile lifestyle.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?