CVE-2021-21216 - Authentication Bypass by Spoofing

Severity

65%

Complexity

27%

Confidentiality

60%

Inappropriate implementation in Autofill in Google Chrome prior to 90.0.4430.72 allowed a remote attacker to spoof security UI via a crafted HTML page.

CVSS 3.1 Base Score 6.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N).

CVSS 2.0 Base Score 4.3. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:N/C:N/I:P/A:N).

Demo Examples

Authentication Bypass by Spoofing

CWE-290

The following code authenticates users.


               
}
authenticated = true;

The authentication mechanism implemented relies on an IP address for source validation. If an attacker is able to spoof the IP, they may be able to bypass the authentication mechanism.

Authentication Bypass by Spoofing

CWE-290

Both of these examples check if a request is from a trusted address before responding to the request.


               
}
}
n = recvfrom(sd, msg, MAX_MSG, 0, (struct sockaddr *) & cli, &clilen);

               
}
}
DatagramPacket sp =new DatagramPacket(out,out.length, IPAddress, port); outSock.send(sp);

The code only verifies the address as stored in the request packet. An attacker can spoof this address, thus impersonating a trusted client

Authentication Bypass by Spoofing

CWE-290

The following code samples use a DNS lookup in order to decide whether or not an inbound request is from a trusted host. If an attacker can poison the DNS cache, they can gain trusted status.


               
}
trusted = true;
trusted = false;

               
}
trusted = true;

               
}
trusted = true;

IP addresses are more reliable than DNS names, but they can also be spoofed. Attackers can easily forge the source IP address of the packets they send, but response packets will return to the forged IP address. To see the response packets, the attacker has to sniff the traffic between the victim machine and the forged IP address. In order to accomplish the required sniffing, attackers typically attempt to locate themselves on the same subnet as the victim machine. Attackers may be able to circumvent this requirement by using source routing, but source routing is disabled across much of the Internet today. In summary, IP address verification can be a useful part of an authentication scheme, but it should not be the single factor required for authentication.

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