Two vulnerabilities have been discovered in the Opera browser, which can be exploited by a malicious person to cause a DoS (Denial of Service) on a user's browser.

Both vulnerabilities are caused due to boundary errors in the handling of filename extensions and can be exploited by a malicious person by constructing a special HTML document, which will make the browser try to download a file with a long filename extension.

The first vulnerability will automatically cause a heap overflow overwriting arbitrary content with the user input converted to 16-bit wide chars.

The second vulnerability will display a download dialog box. If the user agrees to save the file, a stack overflow will be triggered overwriting certain registers (EBP and EIP) with the user input converted to 16-bit wide chars.

It may be possible to exploit the vulnerabilities to compromise a user's system. However, this has not been proven during research.

Solution
Opera Software has released Opera version 7.11 for Windows, which fixes the vulnerabilities. Opera version 7.11 beta 2 for Linux will also be officially released soon.
Further details available to Secunia VIM customers

Provided and/or discovered by
1) Discovered by Jakob Balle, Secunia.

2) The vulnerability was discovered by two different parties around the same time. While Jakob Balle from Secunia was working with the vendor to fix the vulnerability, it was discovered and disclosed on public mailing lists by nesumin before Opera Software had a chance to react.

Changelog
Further details available to Secunia VIM customers

Original Advisory
http://secunia.com/secunia_research/2003-4/

Other references
Further details available to Secunia VIM customers

Deep Links
Links available to Secunia VIM customers