Improper Authentication

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.


The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

The following code intends to ensure that the user is already logged in. If not, the code performs authentication with the user-provided username and password. If successful, it sets the loggedin and user cookies to "remember" that the user has already logged in. Finally, the code performs administrator tasks if the logged-in user has the "Administrator" username, as recorded in the user cookie.

my $q = new CGI;

if ($q->cookie('loggedin') ne "true") {

  if (! AuthenticateUser($q->param('username'), $q->param('password'))) {
    ExitError("Error: you need to log in first");
  else {

    # Set loggedin and user cookies.
      -name => 'loggedin',
      -value => 'true'

      -name => 'user',
      -value => $q->param('username')



if ($q->cookie('user') eq "Administrator") {

Unfortunately, this code can be bypassed. The attacker can set the cookies independently so that the code does not check the username and password. The attacker could do this with an HTTP request containing headers such as:

GET /cgi-bin/vulnerable.cgi HTTP/1.1
Cookie: user=Administrator
Cookie: loggedin=true

[body of request]

By setting the loggedin cookie to "true", the attacker bypasses the entire authentication check. By using the "Administrator" value in the user cookie, the attacker also gains privileges to administer the software.

Example Two

In January 2009, an attacker was able to gain administrator access to a Twitter server because the server did not restrict the number of login attempts [REF-236]. The attacker targeted a member of Twitter's support team and was able to successfully guess the member's password using a brute force attack by guessing a large number of common words. After gaining access as the member of the support staff, the attacker used the administrator panel to gain access to 33 accounts that belonged to celebrities and politicians. Ultimately, fake Twitter messages were sent that appeared to come from the compromised accounts.

Example Three

In 2022, the OT:ICEFALL study examined products by 10 different Operational Technology (OT) vendors. The researchers reported 56 vulnerabilities and said that the products were "insecure by design" [REF-1283]. If exploited, these vulnerabilities often allowed adversaries to change how the products operated, ranging from denial of service to changing the code that the products executed. Since these products were often used in industries such as power, electrical, water, and others, there could even be safety implications.

Multiple vendors did not use any authentication or used client-side authentication for critical functionality in their OT products.

See Also

Comprehensive Categorization: Access Control

Weaknesses in this category are related to access control.

ICS Dependencies (& Architecture): External Digital Systems

Weaknesses in this category are related to the "External Digital Systems" category from the SEI ETF "Categories of Security Vulnerabilities in ICS" as published in Mar...

ICS Communications: Zone Boundary Failures

Weaknesses in this category are related to the "Zone Boundary Failures" category from the SEI ETF "Categories of Security Vulnerabilities in ICS" as published in March...

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses in the 2023 CWE Top 25 Most Dangerous Software Weaknesses

CWE entries in this view are listed in the 2023 CWE Top 25 Most Dangerous Software Weaknesses.

Weaknesses Addressed by ISA/IEC 62443 Requirements

This view (slice) covers weaknesses that are addressed by following requirements in the ISA/IEC 62443 series of standards for industrial automation and control systems...

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