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Vulnerability of IE, Firefox: request splitting via a Digest authentication

Synthesis of the vulnerability 

An attacker can create a malicious web site in order to force web browsers of users behind a proxy to inject a new HTTP query.
Impacted systems: IE, Firefox.
Severity of this alert: 1/4.
Number of vulnerabilities in this bulletin: 2.
Creation date: 26/04/2007.
Références of this alert: BID-23668, CVE-2007-2291, CVE-2007-2292, VIGILANCE-VUL-6767.

Description of the vulnerability 

When HTTP Digest authentication is activated on a web server, it returns to client:
  HTTP/1.1 401 Unauthorized
  WWW-Authenticate: Digest
     realm="realm@server" ...
The web browser then asks user for his login and password, then replies back with:
  Authorization: Digest username="my_user_name",
     realm="realm@server" ...

However, web browsers do not filter line feeds contained in user name. Following uri thus permits to inject line feeds in a HTTP query:
  http://name%0A%0Aend:pass@server/

Consequences of this attack depends on context. For example, when user is behind a proxy, this proxy can send two different queries.
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This computer vulnerability alert impacts software or systems such as IE, Firefox.

Our Vigil@nce team determined that the severity of this computer threat alert is low.

The trust level is of type confirmed by a trusted third party, with an origin of internet server.

This bulletin is about 2 vulnerabilities.

An attacker with a expert ability can exploit this security vulnerability.

Solutions for this threat 

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