Written by Alan Butcher
The Sweet32 vulnerability when detected with a vulnerability scanner will report it as a CVSS 7.5.
CVSS:
CVSS is a scoring system for vulnerability systems, it's an industry standard scoring system to mark findings against a specific number ranging from 0 to 10. They are shown as:
The Sweet32 Vulnerability Information
The Sweet32 vulnerability has been around since 2016, Sweet32 is the name of the attack that was released by a pair of security researchers that were based at the French National Research Institute for Computer Science (INRIA).
Their findings were assigned the CVE’s CVE-2016-2183 and CVE-2016-6329, it was found that the attack takes advantage of a design weakness in some SSL cyphers, the cyphers, are used in common protocols such as TLS, SSH, IPSec and OpenVPN.
The attack makes use of older cyphers which are known to be weaker and offer less protection against attacks, the Sweet32 attack allows an attacker, in certain limited circ*mstances, to recover small portions of plaintext when encrypted with 64-bit block cyphers, such as (3DES and Blowfish).
Block Cyphers
Block cyphers are a type of symmetric algorithm that encrypts plaintext in blocks, as the name implies, rather than bit-by-bit. One of the characteristics of such cyphers is the block length; which determines the size of the chunks into which the plaintext is split and then encrypted. Importantly, the block length of the cypher is independent of the length of the key. So even if you choose a large key size for your encryption, the block length of the cypher can impose its own limitations, and in this case, vulnerabilities.
Remediation
To help protect against this vulnerability, you need to disable some older cyphers in the registry, this can be done as follows:
Disable 3DES
To disable 3DES on your Windows server, set the following registry key:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\Triple DES 168]
“Enabled”=dword:00000000
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