Common Weakness Enumeration

A Community-Developed Dictionary of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors Common Weakness Scoring System
Common Weakness Risk Analysis Framework
Home > CWE List > CWE- Individual Dictionary Definition (2.7)  

Presentation Filter:

CWE-311: Missing Encryption of Sensitive Data

Missing Encryption of Sensitive Data
Weakness ID: 311 (Weakness Base)Status: Draft
+ Description

Description Summary

The software does not encrypt sensitive or critical information before storage or transmission.

Extended Description

The lack of proper data encryption passes up the guarantees of confidentiality, integrity, and accountability that properly implemented encryption conveys.

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



+ Common Consequences

Technical Impact: Read application data

If the application does not use a secure channel, such as SSL, to exchange sensitive information, it is possible for an attacker with access to the network traffic to sniff packets from the connection and uncover the data. This attack is not technically difficult, but does require physical access to some portion of the network over which the sensitive data travels. This access is usually somewhere near where the user is connected to the network (such as a colleague on the company network) but can be anywhere along the path from the user to the end server.

Technical Impact: Modify application data

Omitting the use of encryption in any program which transfers data over a network of any kind should be considered on par with delivering the data sent to each user on the local networks of both the sender and receiver. Worse, this omission allows for the injection of data into a stream of communication between two parties -- with no means for the victims to separate valid data from invalid. In this day of widespread network attacks and password collection sniffers, it is an unnecessary risk to omit encryption from the design of any system which might benefit from it.

+ Likelihood of Exploit

High to Very High

+ Detection Methods

Manual Analysis

The characterizaton of sensitive data often requires domain-specific understanding, so manual methods are useful. However, manual efforts might not achieve desired code coverage within limited time constraints. Black box methods may produce artifacts (e.g. stored data or unencrypted network transfer) that require manual evaluation.

Effectiveness: High

Automated Analysis

Automated measurement of the entropy of an input/output source may indicate the use or lack of encryption, but human analysis is still required to distinguish intentionally-unencrypted data (e.g. metadata) from sensitive data.

+ Demonstrative Examples

Example 1

This code writes a user's login information to a cookie so the user does not have to login again later.

(Bad Code)
Example Language: PHP 
function persistLogin($username, $password){
$data = array("username" => $username, "password"=> $password);
setcookie ("userdata", $data);

The code stores the user's username and password in plaintext in a cookie on the user's machine. This exposes the user's login information if their computer is compromised by an attacker. Even if the user's machine is not compromised, this weakness combined with cross-site scripting (CWE-79) could allow an attacker to remotely copy the cookie.

Also note this example code also exhibits Plaintext Storage in a Cookie (CWE-315).

Example 2

The following code attempts to establish a connection, read in a password, then store it to a buffer.

(Bad Code)
Example Language:
server.sin_family = AF_INET; hp = gethostbyname(argv[1]);
if (hp==NULL) error("Unknown host");
memcpy( (char *)&server.sin_addr,(char *)hp->h_addr,hp->h_length);
if (argc < 3) port = 80;
else port = (unsigned short)atoi(argv[3]);
server.sin_port = htons(port);
if (connect(sock, (struct sockaddr *)&server, sizeof server) < 0) error("Connecting");
while ((n=read(sock,buffer,BUFSIZE-1))!=-1) {


While successful, the program does not encrypt the data before writing it to a buffer, possibly exposing it to unauthorized actors.

Example 3

The following code attempts to establish a connection to a site to communicate sensitive information.

(Bad Code)
Example Language: Java 
try {
URL u = new URL("");
HttpURLConnection hu = (HttpURLConnection) u.openConnection();
OutputStream os = hu.getOutputStream();
catch (IOException e) {

Though a connection is successfully made, the connection is unencrypted and it is possible that all sensitive data sent to or received from the server will be read by unintended actors.

+ Observed Examples
password and username stored in cleartext in a cookie
password stored in cleartext in a file with insecure permissions
chat program disables SSL in some circumstances even when the user says to use SSL.
Chain: product uses an incorrect public exponent when generating an RSA key, which effectively disables the encryption
storage of unencrypted passwords in a database
storage of unencrypted passwords in a database
product stores a password in cleartext in memory
storage of a secret key in cleartext in a temporary file
SCADA product uses HTTP Basic Authentication, which is not encrypted
login credentials stored unencrypted in a registry key
Passwords transmitted in cleartext.
Chain: Use of HTTPS cookie without "secure" flag causes it to be transmitted across unencrypted HTTP.
Product sends password hash in cleartext in violation of intended policy.
Remote management feature sends sensitive information including passwords in cleartext.
Backup routine sends password in cleartext in email.
Product transmits Blowfish encryption key in cleartext.
Printer sends configuration information, including administrative password, in cleartext.
Chain: cleartext transmission of the MD5 hash of password enables attacks against a server that is susceptible to replay (CWE-294).
Product sends passwords in cleartext to a log server.
Product sends file with cleartext passwords in e-mail message intended for diagnostic purposes.
+ Potential Mitigations

Phase: Requirements

Clearly specify which data or resources are valuable enough that they should be protected by encryption. Require that any transmission or storage of this data/resource should use well-vetted encryption algorithms.

Phase: Architecture and Design

Strategy: Threat Modeling

Using threat modeling or other techniques, assume that the data can be compromised through a separate vulnerability or weakness, and determine where encryption will be most effective. Ensure that data that should be private is not being inadvertently exposed using weaknesses such as insecure permissions (CWE-732). [R.311.1]

Phase: Architecture and Design

Ensure that encryption is properly integrated into the system design, including but not necessarily limited to:

  • Encryption that is needed to store or transmit private data of the users of the system

  • Encryption that is needed to protect the system itself from unauthorized disclosure or tampering

Identify the separate needs and contexts for encryption:

  • One-way (i.e., only the user or recipient needs to have the key). This can be achieved using public key cryptography, or other techniques in which the encrypting party (i.e., the software) does not need to have access to a private key.

  • Two-way (i.e., the encryption can be automatically performed on behalf of a user, but the key must be available so that the plaintext can be automatically recoverable by that user). This requires storage of the private key in a format that is recoverable only by the user (or perhaps by the operating system) in a way that cannot be recovered by others.

Phase: Architecture and Design

Strategy: Libraries or Frameworks

When there is a need to store or transmit sensitive data, use strong, up-to-date cryptographic algorithms to encrypt that data. Select a well-vetted algorithm that is currently considered to be strong by experts in the field, and use well-tested implementations. As with all cryptographic mechanisms, the source code should be available for analysis.

For example, US government systems require FIPS 140-2 certification.

Do not develop custom or private cryptographic algorithms. They will likely be exposed to attacks that are well-understood by cryptographers. Reverse engineering techniques are mature. If the algorithm can be compromised if attackers find out how it works, then it is especially weak.

Periodically ensure that the cryptography has not become obsolete. Some older algorithms, once thought to require a billion years of computing time, can now be broken in days or hours. This includes MD4, MD5, SHA1, DES, and other algorithms that were once regarded as strong. [R.311.5]

Phase: Architecture and Design

Strategy: Separation of Privilege

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.

Ensure that appropriate compartmentalization is built into the system design and that the compartmentalization serves to allow for and further reinforce privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide when it is appropriate to use and to drop system privileges.

Phases: Implementation; Architecture and Design

When using industry-approved techniques, use them correctly. Don't cut corners by skipping resource-intensive steps (CWE-325). These steps are often essential for preventing common attacks.

Phase: Implementation

Strategy: Identify and Reduce Attack Surface

Use naming conventions and strong types to make it easier to spot when sensitive data is being used. When creating structures, objects, or other complex entities, separate the sensitive and non-sensitive data as much as possible.

Effectiveness: Defense in Depth

This makes it easier to spot places in the code where data is being used that is unencrypted.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory310Cryptographic Issues
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class693Protection Mechanism Failure
Research Concepts (primary)1000
ChildOfCategoryCategory719OWASP Top Ten 2007 Category A8 - Insecure Cryptographic Storage
Weaknesses in OWASP Top Ten (2007) (primary)629
ChildOfCategoryCategory720OWASP Top Ten 2007 Category A9 - Insecure Communications
Weaknesses in OWASP Top Ten (2007)629
ChildOfCategoryCategory729OWASP Top Ten 2004 Category A8 - Insecure Storage
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory8032010 Top 25 - Porous Defenses
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ChildOfCategoryCategory816OWASP Top Ten 2010 Category A7 - Insecure Cryptographic Storage
Weaknesses in OWASP Top Ten (2010) (primary)809
ChildOfCategoryCategory818OWASP Top Ten 2010 Category A9 - Insufficient Transport Layer Protection
Weaknesses in OWASP Top Ten (2010)809
ChildOfCategoryCategory861CERT Java Secure Coding Section 49 - Miscellaneous (MSC)
Weaknesses Addressed by the CERT Java Secure Coding Standard (primary)844
ChildOfCategoryCategory8662011 Top 25 - Porous Defenses
Weaknesses in the 2011 CWE/SANS Top 25 Most Dangerous Software Errors (primary)900
ChildOfCategoryCategory895SFP Cluster: Information Leak
Software Fault Pattern (SFP) Clusters (primary)888
ChildOfCategoryCategory930OWASP Top Ten 2013 Category A2 - Broken Authentication and Session Management
Weaknesses in OWASP Top Ten (2013)928
ChildOfCategoryCategory934OWASP Top Ten 2013 Category A6 - Sensitive Data Exposure
Weaknesses in OWASP Top Ten (2013) (primary)928
ParentOfWeakness BaseWeakness Base312Cleartext Storage of Sensitive Information
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness BaseWeakness Base319Cleartext Transmission of Sensitive Information
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant614Sensitive Cookie in HTTPS Session Without 'Secure' Attribute
Development Concepts (primary)699
Research Concepts (primary)1000
PeerOfWeakness BaseWeakness Base327Use of a Broken or Risky Cryptographic Algorithm
Research Concepts1000
+ Relationship Notes

There is an overlapping relationship between insecure storage of sensitive information (CWE-922) and missing encryption of sensitive information (CWE-311). Encryption is often used to prevent an attacker from reading the sensitive data. However, encryption does not prevent the attacker from erasing or overwriting the data.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPFailure to encrypt data
OWASP Top Ten 2007A8Insecure Cryptographic Storage
OWASP Top Ten 2007A9Insecure Communications
OWASP Top Ten 2004A8Insecure Storage
WASC4Insufficient Transport Layer Protection
CERT Java Secure CodingMSC00-JUse SSLSocket rather than Socket for secure data exchange
+ References
[R.311.1] [REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". Chapter 9, "Protecting Secret Data" Page 299. 2nd Edition. Microsoft. 2002.
[R.311.2] [REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 17: Failure to Protect Stored Data." Page 253. McGraw-Hill. 2010.
[R.311.3] Frank Kim. "Top 25 Series - Rank 10 - Missing Encryption of Sensitive Data". SANS Software Security Institute. 2010-02-26. <>.
[R.311.4] [REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 2, "Common Vulnerabilities of Encryption", Page 43.. 1st Edition. Addison Wesley. 2006.
[R.311.5] [REF-1] Information Technology Laboratory, National Institute of Standards and Technology. "SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES". 2001-05-25. <>.
+ Content History
Submission DateSubmitterOrganizationSource
Externally Mined
Modification DateModifierOrganizationSource
updated Time_of_Introduction
Suggested OWASP Top Ten 2004 mapping
updated Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
updated Common_Consequences, Other_Notes
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Detection_Factors, Likelihood_of_Exploit, Name, Observed_Examples, Potential_Mitigations, References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings, Time_of_Introduction
updated Related_Attack_Patterns
updated Common_Consequences, Potential_Mitigations, References
updated Potential_Mitigations
updated Demonstrative_Examples, Observed_Examples, Related_Attack_Patterns
updated Demonstrative_Examples
updated Relationships, Taxonomy_Mappings
updated Relationships
updated Potential_Mitigations, Relationships
updated Demonstrative_Examples, References, Relationships, Taxonomy_Mappings
updated Potential_Mitigations, References
updated Relationship_Notes
updated Related_Attack_Patterns
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Failure to Encrypt Data
2010-02-16Failure to Encrypt Sensitive Data
Page Last Updated: June 23, 2014