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Information Exposure Through Discrepancy

ID: 203Date: (C)2012-05-14   (M)2020-09-14
Type: weaknessStatus: INCOMPLETE
Abstraction Type: Class


The product behaves differently or sends different responses in a way that exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.

Applicable Platforms
Language Class: All

Time Of Introduction

  • Architecture and Design
  • Implementation

Common Consequences

ScopeTechnical ImpactNotes
Read application data
Bypass protection mechanism
An attacker can gain access to sensitive information about the system, including authentication information that may allow an attacker to gain access to the system.

Detection Methods

Potential Mitigations

Architecture and Design
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.
 Ensure that error messages only contain minimal details that are useful to the intended audience, and nobody else. The messages need to strike the balance between being too cryptic and not being cryptic enough. They should not necessarily reveal the methods that were used to determine the error. Such detailed information can be used to refine the original attack to increase the chances of success.
If errors must be tracked in some detail, capture them in log messages - but consider what could occur if the log messages can be viewed by attackers. Avoid recording highly sensitive information such as passwords in any form. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a username is valid or not.


Related CWETypeViewChain
CWE-203 ChildOf CWE-895 Category CWE-888  

Demonstrative Examples   (Details)

  1. The following code checks validity of the supplied username and password and notifies the user of a successful or failed login. (Demonstrative Example Id DX-38)

Observed Examples

  1. CVE-2002-2094 : This, and others, use ".." attacks and monitor error responses, so there is overlap with directory traversal.
  2. CVE-2001-1483 : Enumeration of valid usernames based on inconsistent responses
  3. CVE-2001-1528 : Account number enumeration via inconsistent responses.
  4. CVE-2004-2150 : User enumeration via discrepancies in error messages.
  5. CVE-2005-1650 : User enumeration via discrepancies in error messages.
  6. CVE-2004-0294 : Bulletin Board displays different error messages when a user exists or not, which makes it easier for remote attackers to identify valid users and conduct a brute force password guessing attack.
  7. CVE-2004-0243 : Operating System, when direct remote login is disabled, displays a different message if the password is correct, which allows remote attackers to guess the password via brute force methods.
  8. CVE-2002-0514 : Product allows remote attackers to determine if a port is being filtered because the response packet TTL is different than the default TTL.
  9. CVE-2002-0515 : Product sets a different TTL when a port is being filtered than when it is not being filtered, which allows remote attackers to identify filtered ports by comparing TTLs.
  10. CVE-2001-1387 : Product may generate different responses than specified by the administrator, possibly leading to an information leak.
  11. CVE-2004-0778 : Version control system allows remote attackers to determine the existence of arbitrary files and directories via the -X command for an alternate history file, which causes different error messages to be returned.
  12. CVE-2004-1428 : FTP server generates an error message if the user name does not exist instead of prompting for a password, which allows remote attackers to determine valid usernames.
  13. CVE-2003-0078 : SSL implementation does not perform a MAC computation if an incorrect block cipher padding is used, which causes an information leak (timing discrepancy) that may make it easier to launch cryptographic attacks that rely on distinguishing between padding and MAC verification errors, possibly leading to extraction of the original plaintext, aka the "Vaudenay timing attack."
  14. CVE-2000-1117 : Virtual machine allows malicious web site operators to determine the existence of files on the client by measuring delays in the execution of the getSystemResource method.
  15. CVE-2003-0637 : Product uses a shorter timeout for a non-existent user than a valid user, which makes it easier for remote attackers to guess usernames and conduct brute force password guessing.
  16. CVE-2003-0190 : Product immediately sends an error message when a user does not exist, which allows remote attackers to determine valid usernames via a timing attack.
  17. CVE-2004-1602 : FTP server responds in a different amount of time when a given username exists, which allows remote attackers to identify valid usernames by timing the server response.
  18. CVE-2005-0918 : Browser allows remote attackers to determine the existence of arbitrary files by setting the src property to the target filename and using Javascript to determine if the web page immediately stops loading, which indicates whether the file exists or not.

For more examples, refer to CVE relations in the bottom box.

White Box Definitions

Black Box Definitions

Taxynomy Mappings

PLOVER  Discrepancy Information Leaks
OWASP Top Ten 2007 A6
Information Leakage and Improper Error Handling
OWASP Top Ten 2004 A7
Improper Error Handling


CVE    65

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