Common Weakness Enumeration

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CWE-649: Reliance on Obfuscation or Encryption of Security-Relevant Inputs without Integrity Checking

Weakness ID: 649
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software uses obfuscation or encryption of inputs that should not be mutable by an external actor, but the software does not use integrity checks to detect if those inputs have been modified.

Extended Description

When an application relies on obfuscation or incorrectly applied / weak encryption to protect client-controllable tokens or parameters, that may have an effect on the user state, system state, or some decision made on the server. Without protecting the tokens/parameters for integrity, the application is vulnerable to an attack where an adversary blindly traverses the space of possible values of the said token/parameter in order to attempt to gain an advantage. The goal of the attacker is to find another admissible value that will somehow elevate his or her privileges in the system, disclose information or change the behavior of the system in some way beneficial to the attacker. If the application does not protect these critical tokens/parameters for integrity, it will not be able to determine that these values have been tampered with. Measures that are used to protect data for confidentiality should not be relied upon to provide the integrity service.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms



+ Common Consequences

Technical Impact: Unexpected state

The inputs could be modified without detection, causing the software to have unexpected system state or make incorrect security decisions.

+ Likelihood of Exploit


+ Enabling Factors for Exploitation

The application uses client controllable tokens/parameters in order to make decisions on the server side about user state, system state or other decisions related to the functionality of the application.

The application does not protect client controllable tokens/parameters for integrity and thus not able to catch tampering.

+ Observed Examples
An IPSec configuration does not perform integrity checking of the IPSec packet as the result of either not configuring ESP properly to support the integrity service or using AH improperly. In either case, the security gateway receiving the IPSec packet would not validate the integrity of the packet to ensure that it was not changed. Thus if the packets were intercepted the attacker could undetectably change some of the bits in the packets. The meaningful bit flipping was possible due to the known weaknesses in the CBC encryption mode. Since the attacker knew the structure of the packet, he or she was able (in one variation of the attack) to use bit flipping to change the destination IP of the packet to the destination machine controlled by the attacker. And so the destination security gateway would decrypt the packet and then forward the plaintext to the machine controlled by the attacker. The attacker could then read the original message. For instance if VPN was used with the vulnerable IPSec configuration the attacker could read the victim's e-mail. This vulnerability demonstrates the need to enforce the integrity service properly when critical data could be modified by an attacker. This problem might have also been mitigated by using an encryption mode that is not susceptible to bit flipping attacks, but the preferred mechanism to address this problem still remains message verification for integrity. While this attack focuses on the network layer and requires a man in the middle scenario, the situation is not much different at the software level where an attacker can modify tokens/parameters used by the application.
+ Potential Mitigations

Phase: Architecture and Design

Protect important client controllable tokens/parameters for integrity using PKI methods (i.e. digital signatures) or other means, and checks for integrity on the server side.

Phase: Architecture and Design

Repeated requests from a particular user that include invalid values of tokens/parameters (those that should not be changed manually by users) should result in the user account lockout.

Phase: Architecture and Design

Client side tokens/parameters should not be such that it would be easy/predictable to guess another valid state.

Phase: Architecture and Design

Obfuscation should not be relied upon. If encryption is used, it needs to be properly applied (i.e. proven algorithm and implementation, use padding, use random initialization vector, user proper encryption mode). Even with proper encryption where the ciphertext does not leak information about the plaintext or reveal its structure, compromising integrity is possible (although less likely) without the provision of the integrity service.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class345Insufficient Verification of Data Authenticity
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory975SFP Secondary Cluster: Architecture
Software Fault Pattern (SFP) Clusters (primary)888
+ Content History
Submission DateSubmitterOrganizationSource
2008-01-30Evgeny LebanidzeCigitalExternal Submission
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITREInternal
updated Common_Consequences, Relationships, Observed_Example
2008-10-14CWE Content TeamMITREInternal
updated Description
2009-10-29CWE Content TeamMITREInternal
updated Common_Consequences
2010-12-13CWE Content TeamMITREInternal
updated Common_Consequences, Description, Enabling_Factors_for_Exploitation, Observed_Examples
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Related_Attack_Patterns, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Relying on Obfuscation or Encryption with no Integrity Checking to Protect User Controllable Parameters that are Used to Determine User or System State

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Page Last Updated: May 05, 2017