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The Opera browser exhibits a failure when rendering HTML. Certain HREFs cause a buffer allocated on the heap to overflow. Arbitrary bytes in the heap may be overwritten. This can result in the compromise of systems running Opera. Opera's mail system seems to be vulnerable also and recovery from reading an email is somewhat difficult.
An attacker can send an email containing HTML to a user running the Opera mail client and cause this overflow to occur when the HTML is rendered. An owner of a web site can craft a malicious web page containing the problematic HTML to cause an overflow on Opera clients visiting the site. |
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Credit:
The original advisory can be downloaded from: http://www.atstake.com/research/advisories/2003/a102003-1.txt.
The information has been provided by at stake Advisories.
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Vulnerable systems:
* Opera version 7.11
* Opera version 7.20
Immune systems:
* Opera version 7.21
Rendering HREFs with certain illegally escaped server names in the URL will cause Opera to crash due to a buffer management problem. Sometimes the crash is observed immediately, sometimes when the browser is closed, presumably as the resources are being freed.
The escaped URLs are of the form:
<a href="file://server%%[many % characters]%%text" ></a>
Vendor Response:
Opera has release a new version of the software that is available here: http://www.opera.com/download/
The change log (http://www.opera.com/windows/changelogs/721/) notes this fix as:
"Fixed a crash caused by illegally escaped server name"
There is no specific bulletin or warning to users that this release contains security fixes.
Recommendation:
Upgrade to the 7.21 version of Opera browser for your platform. Filter email to remove HTML. Run your web browser and mail client as a low privileged user.
Timeline:
09/29/2003 Opera contacted with details of issue
09/30/2003 Vendor responds that they have reproduced problem
10/15/2003 Vendor releases new version of program that includes a fix
10/20/2003 Advisory released
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