Firefox deprecated ciphers must be disabled.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-251571	SRG-APP-000141	FFOX-00-000027	SV-251571r960963_rule	2025-02-11	6

Description
A weak cipher is defined as an encryption/decryption algorithm that uses a key of insufficient length. Using an insufficient length for a key in an encryption/decryption algorithm opens up the possibility (or probability) that the encryption scheme could be broken.

ℹ️ Check
Type "about:policies" in the browser address bar. If "DisabledCiphers" is not displayed under Policy Name or the Policy Value is not "TLS_RSA_WITH_3DES_EDE_CBC_SHA" with a value of "true", this is a finding.

✔️ Fix
Windows group policy: 1. Open the group policy editor tool with "gpedit.msc". 2. Navigate to Policy Path: Computer Configuration\Administrative Templates\Mozilla\Firefox\Disabled Ciphers Policy Name: TLS_RSA_WITH_3DES_EDE_CBC_SHA Policy State: Enabled macOS "plist" file: Add the following: <key>DisabledCiphers</key> <dict> <key>TLS_RSA_WITH_3DES_EDE_CBC_SHA</key> <true/> </dict> Linux "policies.json" file: Add the following in the policies section: "DisabledCiphers": { "TLS_RSA_WITH_3DES_EDE_CBC_SHA": true }

✔️ Fix

Windows group policy: 1. Open the group policy editor tool with "gpedit.msc". 2. Navigate to Policy Path: Computer Configuration\Administrative Templates\Mozilla\Firefox\Disabled Ciphers Policy Name: TLS_RSA_WITH_3DES_EDE_CBC_SHA Policy State: Enabled macOS "plist" file: Add the following: <key>DisabledCiphers</key> <dict> <key>TLS_RSA_WITH_3DES_EDE_CBC_SHA</key> <true/> </dict> Linux "policies.json" file: Add the following in the policies section: "DisabledCiphers": { "TLS_RSA_WITH_3DES_EDE_CBC_SHA": true }