Crash Google Chrome with one tiny URL: We cram a probe in this bug
How clicking on or even rolling your mouse over it will knacker browser
You can crash the latest version of Google Chrome with a simple tiny URL.
Just rolling your mouse over it in a page, launching it from another app such as an email client, or pasting it into the address bar, will kill either that tab or the whole browser.
It's perfect for pranking friends by sending it to them in emails and messages.
This crashes someone's browser in web gtalk/chrome if you msg them that URL https://t.co/vi0e10IEFH— mdowd (@mdowd) September 20, 2015
Below is a screenshot of two forms of the offending URL – we won't put them this article as-is, because they will crash your tab if you accidentally wander your pointer over them in Chrome. And that's not nice.
We've tested it on Chrome 45.0.2454.93 on OS X El Capitan and Windows 10, and both flavors of the browser are vulnerable. Chromebooks and Linux flavors of the browser are also crashed by the URL, plus Opera 32.0 which is based on Chromium 45, we're told. Android's Chrome is not affected, it seems.
"Unfortunately no reward was awarded as this was deemed to be only a denial-of-service vulnerability," wrote Atteka. "Anyway, making secure software is much harder than finding issues in it. Thanks Google."
What's cool about this bug is that it triggers a fatal exception (a SIGTRAP) rather than the usual memory access violation error caused by an overrun buffer, heap corruption, or similar – even in released code. This means some part of the executable was reached that the programmers never expected normal users to hit. As it turns out, the code at fault is some really old stuff.
This is the crash information from OS X:
Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x0000000000000002, 0x0000000000000000 Thread 0 Crashed:: CrBrowserMain Dispatch queue: com.apple.main-thread 0 com.google.Chrome.framework 0x0000000102b18a45 0x102500000 + 6392389 1 com.google.Chrome.framework 0x0000000105900595 0x102500000 + 54527381 2 com.google.Chrome.framework 0x00000001059083d2 0x102500000 + 54559698
What happens is this:
%%300at the end of the URL is converted into
0x30is the ASCII code for '0'. The
%%300becomes this string of characters: the original '%', the converted '0', and the original '0'. Combined, that's '%00'.) This sticks a NULL byte at the end of the web address.
- This URL is passed to
- This causes the URL to be processed again, hitting the NULL byte. It figures that shouldn't be there and marks the URL as invalid.
- The code path returns to
GURLToDatabaseURL()which expects the URL to still be valid, and calls
- But the URL is invalid, which is unexpected, and so the function hits a
DCHECK() that causes the software to bail out – even on the release build.
- When hovering the mouse over the URL, the web address, which is marked as invalid, is sent to another part of the browser that expects valid-only addresses – causing the tab to be blown away.
"There are going to be crashes all over as a result of this. This is a mess," sighed one Chromium project contributor a couple of hours ago. The team are working on a fix, so stay tuned. ®
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