Here's a dillema:
On one side you want to keep your machine up to date with all latest patches, but then there is "Cumulative Security Update for Internet Explorer (832894)", which disables the user:pass@ way of authentication.
Now, do you update and loose this functionality (which can be handy), or don't apply it but have the other security it fixes unpatched?
Here's what I did:
But I really, really wanted the user:pass back, and it's even in an RFC MS has linked.
3.1. Common Internet Scheme Syntax
While the syntax for the rest of the URL may vary depending on the
particular scheme selected, URL schemes that involve the direct use
of an IP-based protocol to a specified host on the Internet use a
common syntax for the scheme-specific data:
Some or all of the parts "<user>:<password>@", ":<password>",
":<port>", and "/<url-path>" may be excluded. The scheme specific
data start with a double slash "//" to indicate that it complies with
the common Internet scheme syntax. The different components obey the
An optional user name. Some schemes (e.g., ftp) allow the
specification of a user name.
An optional password. If present, it follows the user
name separated from it by a colon.
The user name (and password), if present, are followed by a
commercial at-sign "@". Within the user and password field, any ":",
"@", or "/" must be encoded.
The solution? Re-enable it!
to re-enable it for the entire machine,
or go to:
to re-enable it for the logged in user.
Now create iexplore.exe and explorer.exe DWORD values and set their value data to 0.
Done, you just got the user:pass@ functionality back.
As Kent Sharkey writes, the RFC I quoted actually did not specifiy the user:pass possibilty for the HTTP protocol. I'm sorry for that, it's a 'feature' I guess :)
This registry tweak does however not undo the patch, it only reactivates this 'feature', the chr(0) exploit remains fixed with this tweak.
Here is a .reg file to re-enable it system-wide.