The product stores sensitive information in cleartext in a cookie.
Attackers can use widely-available tools to view the cookie and read the sensitive information. Even if the information is encoded in a way that is not human-readable, certain techniques could determine which encoding is being used, then decode the information.

Primary

Architecture and Design
OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.

Confidentiality
Read Application Data

Automated Static Analysis
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
High

The following code excerpt stores a plaintext user account ID in a browser cookie.

response.addCookie( new Cookie("userAccountID", acctID) );

Because the account ID is in plaintext, the user's account information is exposed if their computer is compromised by an attacker.

CVE-2002-1800
Admin password in cleartext in a cookie.
https://www.cve.org/CVERecord?id=CVE-2002-1800

CVE-2001-1537
Default configuration has cleartext usernames/passwords in cookie.
https://www.cve.org/CVERecord?id=CVE-2001-1537

CVE-2001-1536
Usernames/passwords in cleartext in cookies.
https://www.cve.org/CVERecord?id=CVE-2001-1536

CVE-2005-2160
Authentication information stored in cleartext in a cookie.
https://www.cve.org/CVERecord?id=CVE-2005-2160

Plaintext Storage in Cookie

SFP23
Exposed Data

Allowed
This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Different people use "cleartext" and "plaintext" to mean the same thing: the lack of encryption. However, within cryptography, these have more precise meanings. Plaintext is the information just before it is fed into a cryptographic algorithm, including already-encrypted text. Cleartext is any information that is unencrypted, although it might be in an encoded form that is not easily human-readable (such as base64 encoding).

PLOVER
2006-07-19
Draft 3
2006-07-19

Sean Eidemiller
Cigital
2008-07-01
added/updated demonstrative examples

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Demonstrative_Examples, Relationships

CWE Content Team
MITRE
2013-07-17
updated Applicable_Platforms, Demonstrative_Examples, Description, Name, Observed_Examples, Potential_Mitigations, Terminology_Notes

CWE Content Team
MITRE
2014-07-30
updated Demonstrative_Examples, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2017-11-08
updated Modes_of_Introduction, Relationships

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated Detection_Factors, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Relationships, Weakness_Ordinalities

Camille Gouttebroze
CAST Software
2024-10-28
4.17
2025-04-03
reported a syntax error in demox 1

Plaintext Storage in Cookie
Plaintext Storage in a Cookie