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New Firefox Vulnerability Revealed
Not long after Firefox 3.5.1 was released to address a security issue, a new exploit has been found and a proof of concept has been posted. "The vulnerability is a remote stack-based buffer-overflow, triggered by sending an overly long string of Unicode data to the document.write method. If exploited, the resulting overflow could lead to code execution, or if the exploit attempts fail, a denial-of-service scenario." It's recommended that Firefox users disable Javascript until the issue is patched, though add-ons like NoScript should do the trick as well (unless a site on your whitelist becomes compromised).
Update: 07/20 00:09 GMT by KD : An anonymous reader informs us that the Mozilla security blog is indicating that this vulnerability is not exploitable; denial of service is as bad as it gets.
Update: 07/20 00:09 GMT by KD : An anonymous reader informs us that the Mozilla security blog is indicating that this vulnerability is not exploitable; denial of service is as bad as it gets.
So who's the moron using unbounded buffers?
Great minds think alike; fools seldom differ.
Is this a new copy-and-paste troll? Almost the same post appeared in the Linux kernel exploit article. Apparently some people missed the Defective by Design campaign and are completely unaware that it relates to DRM, not to arbitrary bugs.
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I don't know anything about JavaScript or Firefox internals, but a public sounding central function call like "DOCUMENT.WRITE" having a length related buffer overflow is just unacceptable. This call is used all the time right? How could this be missed?
Let's just hope that all those eyes are friendly. How many black hats are scouring the source code to generate exploits to sell underground? As quickly as Firefox releases patches, when these bugs aren't reported it's no better than a proprietary browser.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
FTFA: The vulnerability was reported to SecurityFocus (BID 35707) on July 15.
4 days > 24 hours.
It looks like the proof of concept only shows how this could lead to a stack overflow. There is no concept about how this could lead to code execution, which makes this just just another way to crash a browser.
Crashing browsers is of course potentially a problem, but it quite boring while there are still so many ways to do real exploits.
document.write = function(){ alert("This website was designed by a fucking idiot."); };
http://slashdot.org/tags/defectivebydesign
Some stories tagged "defectivebydesign" that are not at all related to DRM:
"Critical Security Hole in Linux Wi-Fi" .MOV + Toshiba + Vista = BSOD"
"Apple Issues Patches For 25 Security Holes"
""Very Severe Hole" In Vista UAC Design"
"MS Responds To Vista's Network / Audio Problems"
"Apple's IPhone 3G Firmware Update Bombs"
"QuickTime
"Vista Slow To Copy, Delete Files"
"Vista Runs Out of Memory While Copying Files"
"Mark Russinovich On Vista Network Slowdown"
"Microsoft Knew About Xbox 360 Damaging Discs"
"Vista Not Playing Nice With FPS Games"
That's as far as I can be bothered to read. Go look at it yourself. That tag is cheerfully applied to many, many stories about Windows or Apple bugs.
The proof of concept has crashed every browser I've tried it on; Firefox (obviously) (and the 3.6 nightly), Epiphany, Chromium, Opera and Android Browser. So is Firefox the only browser that is exploitable during the crash or other browsers affected?
If you use firefox, then you are the moron using unbounded buffers.
These recurring requests to turn off something are getting annoying. Why not automate the process? Set up a page somewhere like
www.mozilla.com/firefox/3.5.1/current-safety.txt
which would list something like
javascript: unsafe
java: safe
flash: safe
Then by default your browser would fetch that file and automatically implement Mozilla's recommendation of the day.
The primary difference being that bugs like this Firefox flaw are accidental and unintentional, whereas DRM is quite deliberate hence the "defective by design" nomenclature. That's such a sharp contrast, it's reasonable to assume that someone who fails to notice it is either speaking of what they know nothing about or purposely trolling. In other words, "highly advanced incompetence is indistinguishable from malice."
There were two ideas mentioned by GP, which were the "defective by design" label and the security reputation of IE. It's useful to know where those perceptions come from whether or not you actually agree with them. I'll make a very simplified (and therefore imperfect) summary of what I perceive as their bases.
The only reason why I see such a concept as "defective by design" applied to IE is a vague one. IE (and Microsoft in general) has something of a history of implementing ideas that were predictably unsound, the most notorious of which is probably ActiveX. That's mostly because ideas which are computationally sound are often orthogonal to ideas which are most easily marketed. True to the nature of a corporation, whenever these two are in conflict, the marketing concerns will win. This is where that perception of closed-source (that is, commercial) software that the GP mentioned comes from.
ActiveX is running untrusted code from a hostile network with no sandboxing and with the full privileges of the user running the browser. Before a single line of code is ever written to implement this, you can predict in advance that this is an unsound idea which invites trouble. Microsoft wrote the code and implemented the idea anyway. IMO that was a deliberate business decision because they felt the marketing and promotion of $SHINY_FEATURE would gain them more than they would lose from the PR problems of security issues. Because of how ignorant the general public tends to be about computer security, such decision-making has been largely successful. In other words, the people at Microsoft are not a bunch of idiots who didn't know what they were dealing with. They knew and they made their decision. Still, it's better to call that "faulty design" and "poor priorities" than to hijack a very specific term like "defective by design."
It is a miracle that curiosity survives formal education. - Einstein
Have you tried the POC? Ideally under a debugger? It's a null-dereference crash due to failure to check an allocation for out-of-memory conditions. It's not exploitable, as far as I can see. And it's not a stack buffer overflow, by any means.
It'd be nice if these various security advisory services actually double-checked milw0rm postings before echoing them. Half the ones I've seen are in fact crashes, but not the sort the poster claims and not exploitable....
A simple heuristic: if you can submit a well-written bug report and at least an attempt is made to fix the issue, it's probably not a design flaw.
It is a miracle that curiosity survives formal education. - Einstein
Fix once, fix forever
The bug is in the Just-in-Time compiler inside of SpiderMonkey (TraceMonkey). This is brand new code as of 3.5.x. Of course there will be a ton of bugs found in it (just like the ton of bugs that have cropped up in SquirrelFish and have been subsequently patched).
I have to wonder why it's taken so long for anybody's security team to look at this code though. You'd think they'd look at this code before release and not after.
"Victory means exit strategy, and it's important for the President to explain to us what the exit strategy is." G.W.Bush
This is the reason why I avoid crappy software like Firefox and stick to MSIE! Firefox is riddled with bad, bloated code making it easily subjectable to these types of attacks. On top of that, the development model allows mistakes like this to get into the codebase without proper quality assurance.
If I have to /sarcasm, I will kill you.
Whoever modded the parent as troll is a moron. Offtopic maybe, but not troll. Go ahead and mod me down too.
The parent is right. I've had my paranoid period and tried NoScript; the web was so damn broken, and clicking to allow JS over and over again turned so tiresome that I turned to everything whitelisted by default, and finally uninstalled NoScript after the AdBlock fiasco.
About how bad of a language JavaScript is or isn't: I personally like it, though I'd prefer Lua, or say, Python; but JS is here to stay and it serves its purpose. Except that purpose isn't replacing HTML, or turning HTTP into something it was never meant to be. Back when I was coding JS, we were doing it to improve the user experience, not replace it altogether. Nowadays "web developers" use [insert random JS framework] for everything, but the problem is so, so many use it in braindead ways. You middle click on a thumbnail expecting to open the image in a new tab, but you just get the same page with a nice # added at the end. And then there's the idiots doing <a href="javascript:">, and the utter idiots with an attitude that do onclick="submit_something_via_post" and figure out they know better how the web is supposed to work... These are usually the same idiots that will do broken browser detection based on the User-Agent string, and usually fail miserably if your browser sends along "Gecko", but not "Firefox". Say, something like "Iceweasel". For a nice example of how far this stupidity goes, try browsing VIA's site.
You want to use XHR when clicking on a link? Or submitting a form? That's all fine and dandy, but don't break the web. It's becoming more and more like flash, with the sole difference you can view-source.
If you're building Google Docs or Meebo, all hail JavaScript. But for mostly everything else, lack of graceful degradation with JS disabled is pure idiocy. Not just because there's paranoid people browsing with JS disabled, but because there's blind people using the web, and people with antiquated handhelds, or simply stuck in a console trying to fix nvidia's latest fuck-up. Of course, it would take building the site / web app properly from the bottom up: HTML, server interaction, CSS, JavaScript. But the "developers" these day start with YUI or Dojo: some shiny animation is the end purpose in on itself, not an improvement to conveying information.
By the way: did you try GMail with JS disabled? It works. It probably works in lynx too, since it works in elinks just fine. That's the way JS is supposed to be used.
</rant>
See what Mozilla has to say: http://blog.mozilla.com/security/2009/07/19/milw0rm-9158-stack-overflow-crash-not-exploitable-cve-2009-2479/ In the last few days, there have been several reports (including one via SANS) of a bug in Firefox related to handling of certain very long Unicode strings. While these strings can result in crashes of some versions of Firefox, the reports by press and various security agencies have incorrectly indicated that this is an exploitable bug. Our analysis indicates that it is not, and we have seen no example of exploitability. On Windows, Firefox 3.0.x is terminated due to an uncaught exception during an attempt to allocate a very large string buffer; this termination is safe and immediate, and does not permit the execution of attacker code. In Firefox 3.5.x on Windows, the allocations are more robustly checked and no crash will result. On the Macintosh in Firefox 3.0.x and 3.5.x, a crash occurs inside the ATSUI system library (part of OS X), due to what appears to be a failure to check allocation results. This issue is likely to affect any application using the recommended text-handling libraries on OS X. We have reported this issue to Apple, but in the event that they do not provide a fix we will look to implement mitigations in Mozilla code. We recommend that other developers who use these libraries consider a similar practice, and we have added mitigations in the past for similar bugs in these libraries. As a result of our analysis, we do not believe that this represents an exploitable vulnerability in Firefox. Further, we believe that the IBM report is in error, and that the severity rating in the National Vulnerability Database report is incorrect. We have contacted them and hope to resolve the inaccuracies shortly.