Description

A protocol or its implementation supports interaction between multiple actors and allows those actors to negotiate which algorithm should be used as a protection mechanism such as encryption or authentication, but it does not select the strongest algorithm that is available to both parties.

Extended Description

When a security mechanism can be forced to downgrade to use a less secure algorithm, this can make it easier for attackers to compromise the software by exploiting weaker algorithm. The victim might not be aware that the less secure algorithm is being used. For example, if an attacker can force a communications channel to use cleartext instead of strongly-encrypted data, then the attacker could read the channel by sniffing, instead of going through extra effort of trying to decrypt the data using brute force techniques.

Applicable Platforms
None

Related Attack Patterns

• CAPEC-220

Common Consequences

Detection Methods
None

Potential Mitigations
None

Relationships
This is related to CWE-300 (Man-in-the-Middle), although not all downgrade attacks necessarily require a man in the middle. See examples.

Demonstrative Examples
None

Observed Examples

1. CVE-2006-4302 : Attacker can select an older version of the software to exploit its vulnerabilities.
2. CVE-2006-4407 : Improper prioritization of encryption ciphers during negotiation leads to use of a weaker cipher.
3. CVE-2005-2969 : chain: SSL/TLS implementation disables a verification step (CWE-325) that enables a downgrade attack to a weaker protocol.
4. CVE-2001-1444 : Telnet protocol implementation allows downgrade to weaker authentication and encryption using a man-in-the-middle attack.
5. CVE-2002-1646 : SSH server implementation allows override of configuration setting to use weaker authentication schemes. This may be a composite with CWE-642.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings
None

References:
None