CWE

CWE-203 – Observable Discrepancy

Read Time:3 Minute, 36 Second

Description

The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.

Discrepancies can take many forms, and variations may be detectable in timing, control flow, communications such as replies or requests, or general behavior. These discrepancies can reveal information about the product’s operation or internal state to an unauthorized actor. In some cases, discrepancies can be used by attackers to form a side channel.

Modes of Introduction:

– Architecture and Design

 

 

Related Weaknesses

CWE-200
CWE-200

 

Consequences

Confidentiality, Access Control: 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.

Confidentiality: Read Application Data

When cryptographic primitives are vulnerable to side-channel-attacks, this could be used to reveal unencrypted plaintext in the worst case.

 

Potential Mitigations

Phase: Architecture and Design

Description: 

Phase: Implementation

Description: 

CVE References

  • CVE-2020-8695
    • Observable discrepancy in the RAPL interface for some Intel processors allows information disclosure.
  • CVE-2002-2094
    • This, and others, use “..” attacks and monitor error responses, so there is overlap with directory traversal.
  • CVE-2001-1483
    • Enumeration of valid usernames based on inconsistent responses
  • CVE-2001-1528
    • Account number enumeration via inconsistent responses.
  • CVE-2004-2150
    • User enumeration via discrepancies in error messages.
  • CVE-2005-1650
    • User enumeration via discrepancies in error messages.
  • 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.
  • 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.
  • 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.
  • 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.
  • CVE-2002-0208
    • Product modifies TCP/IP stack and ICMP error messages in unusual ways that show the product is in use.
  • CVE-2004-2252
    • Behavioral infoleak by responding to SYN-FIN packets.
  • CVE-2001-1387
    • Product may generate different responses than specified by the administrator, possibly leading to an information leak.
  • 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.
  • 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.
  • 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.”
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.