A Browser Flaw a Day Keeps Hackers at Play

A well-known hacker has stockpiled browser exploits and plans to release one flaw a day for the month of July to highlight the types of vulnerabilities affecting the worlds most widely used Web browsers.

HD Moore, co-founder of the Metasploit Framework, has launched a new project called MoBB (Month of Browser Bugs) with daily releases of proof-of-concept code for flaws in Internet Explorer, Firefox, Safari, Opera and Konqueror.

“We will publish a new browser hack, every day, for the entire month of July. The hacks we publish are carefully chosen to demonstrate a concept without disclosing a direct path to remote code execution,” Moore said in a blog entry announcing the project.

So far, four flaw warnings have been posted with accompanying exploit code. Three of the four pertain to Microsofts dominant IE browser.

According to Moore, two of the IE bugs remain unpatched although they were reported to Microsoft on March 6, almost four months ago.

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The other alert addresses a bug in Mozillas Firefox, but Moore noted that this has already been fixed in newer versions of the open-source browser.

Moore, who is renowned in security circles for his work regarding penetration testing and exploit creation, has recently turned his attention to Web browsers, collaborating on several fuzz-testing tools aimed at finding design flaws.

Fuzz testers, or fuzzers, are used by security researchers to find vulnerabilities by sending random input to an application. If the program contains a vulnerability that leads to an exception, crash or server error, researchers can parse the results of the test to pinpoint the cause of the crash.

Moore has collaborated on three browser fuzzers—Hamachi, CSS-Die and DOM-Hanai—that have been used to put the major browsers through the security testing mill.

Hamachi, for example, is a utility that attempts to verify browser integrity by looking for common DHTML (Dynamic HTML) implementation flaws. The tool specifies common “bad” values for method arguments and property values. During tests, Moore noted that Firefox 1.5.0.1 passed all Hamachi tests without crashing.

CSS-Die looks for common CSS1/CSS2/CSS3 (Cascading Style Sheets) implementation flaws while DOM-Hanoi is programmed to look for common DHTML implementation flaws by adding/removing DOM (Document Object Model) elements.

The findings have been startling. “We could probably release one a day for the next two and a half years without running out of bugs,” Moore said.

Microsoft typically downgrades reports of browser crashes, treating those as stability issues that get fixed in service packs instead of via monthly security updates.

The strategy of treating denial-of-service bugs as low-priority issues backfired in a major way in November 2005 when an IE JavaScript Window() flaw was improperly diagnosed as a browser crash.

Several months after that bug was reported to Microsoft, a British group called “Computer Terrorism” posted detailed exploit code for it that could have been used by a remote hacker to take complete control of a fully patched Windows system.

“Just about any application-crash vulnerability can be turned into arbitrary code execution, if someone is determined enough to work at it,” said Roger Thompson, chief technical officer at Exploit Prevention Labs, in Atlanta.

Thompson, a veteran anti-virus researcher, said he believes Moores MoBB project can help users to test PCs and defense systems, but he warned of a dangerous downside.

“The bad guys watch for these announcements too, and it provides, if not a road map for them, a really good clue about how to exploit the vulnerability,” Thompson said.

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