CVE-2018-8435 - Insufficient Entropy

Severity

23%

Complexity

44%

Confidentiality

48%

A security feature bypass vulnerability exists when Windows Hyper-V BIOS loader fails to provide a high-entropy source, aka "Windows Hyper-V Security Feature Bypass Vulnerability." This affects Windows Server 2016, Windows 10, Windows 10 Servers.

A security feature bypass vulnerability exists when Windows Hyper-V BIOS loader fails to provide a high-entropy source, aka "Windows Hyper-V Security Feature Bypass Vulnerability." This affects Windows Server 2016, Windows 10, Windows 10 Servers.

CVSS 3.0 Base Score 4.2. CVSS Attack Vector: adjacent_network. CVSS Attack Complexity: high. CVSS Vector: (CVSS:3.0/AV:A/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N).

CVSS 2.0 Base Score 2.3. CVSS Attack Vector: adjacent_network. CVSS Attack Complexity: medium. CVSS Vector: (AV:A/AC:M/Au:S/C:N/I:P/A:N).

Demo Examples

Insufficient Entropy

CWE-331

This code generates a unique random identifier for a user's session.


               
}
return rand();

Because the seed for the PRNG is always the user's ID, the session ID will always be the same. An attacker could thus predict any user's session ID and potentially hijack the session.

This example also exhibits a Small Seed Space (CWE-339).

Insufficient Entropy

CWE-331

The following code uses a statistical PRNG to create a URL for a receipt that remains active for some period of time after a purchase.


               
}
return(baseUrl + ranGen.nextInt(400000000) + ".html");

This code uses the Random.nextInt() function to generate "unique" identifiers for the receipt pages it generates. Because Random.nextInt() is a statistical PRNG, it is easy for an attacker to guess the strings it generates. Although the underlying design of the receipt system is also faulty, it would be more secure if it used a random number generator that did not produce predictable receipt identifiers, such as a cryptographic PRNG.

Overview

Type

Microsoft Windows

First reported 6 years ago

2018-09-13 00:29:00

Last updated 5 years ago

2019-10-03 00:03:00

Affected Software

Microsoft Windows 10 64-bit

Microsoft Windows 10 1607 64-bit

1607

Microsoft Windows 10 1703 64 bit

1703

Microsoft Windows 10 1709 64 bit

1709

Microsoft Windows 10 1803 on x64

1803

Microsoft Windows Server 2016

Microsoft Windows Server 2016 1709

1709

Microsoft Windows Server 2016 1803

1803

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