Weak Ciphers Enabled
Summary#
Invicti detected that weak ciphers are enabled during secure communication (SSL).
You should allow only strong ciphers on your web server to protect secure communication with your visitors.
Impact#
Attackers might decrypt SSL traffic between your server and your visitors.
Actions To Take#
- For Apache, you should modify the SSLCipherSuite directive in the
httpd.conf.SSLCipherSuite HIGH:MEDIUM:!MD5:!RC4
- Lighttpd:
ssl.honor-cipher-order = "enable" ssl.cipher-list = "EECDH+AESGCM:EDH+AESGCM"
- For Microsoft IIS, you should make some changes to the system registry. Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on your computer.
a. Click Start, click Run, typeregedt32or typeregedit, and then click OK.
b. In Registry Editor, locate the following registry key:HKLMSYSTEMCurrentControlSetControlSecurityProviders
c. Set "Enabled" DWORD to "0x0" for the following registry keys:
SCHANNELCiphersDES 56/56
You may also use the
SCHANNELCiphersRC4 64/128
SCHANNELCiphersRC4 40/128
SCHANNELCiphersRC2 56/128
SCHANNELCiphersRC2 40/128
SCHANNELCiphersNULL
SCHANNELHashesMD5Disable-TlsCipherSuitepowershell command to disable certain ciphers.Disable-TlsCipherSuite -Name "TLS_RSA_WITH_AES_256_CBC_SHA"
To get a formatted list of ciphers, you can use the following command.Get-TlsCipherSuite | Format-Table Name
Remediation#
Configure your web server to disallow using weak ciphers. Please consider following when selecting ciphers:
- Use at least 128 bit of encryption
- Anonymous Diffie-Hellman (ADH) suites do not provide authentication.
- Using CBC ciphers, Export ciphers, NULL cipher suites is insecure.
- RC4 is insecure.
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