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curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to MITM a connection due to bad handling of TLS 1.3 session tickets. When using a HTTPS proxy and TLS 1.3, libcurl can confuse session tickets arriving from the HTTPS proxy but work as if they arrived from the remote server and then wrongly "short-cut" the host handshake. When confusing the tickets, a HTTPS proxy can trick libcurl to use the wrong session ticket resume for the host and thereby circumvent the server TLS certificate check and make a MITM attack to be possible to perform unnoticed. Note that such a malicious HTTPS proxy needs to provide a certificate that curl will accept for the MITMed server for an attack to work - unless curl has been told to ignore the server certificate check.
CVSS 3.1 Base Score 3.7. CVSS Attack Vector: network. CVSS Attack Complexity: high. CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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).
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.
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
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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