CVE-2023-26136 in tough-cookie
Summary
by MITRE • 07/01/2023
Versions of the package tough-cookie before 4.1.3 are vulnerable to Prototype Pollution due to improper handling of Cookies when using CookieJar in rejectPublicSuffixes=false mode. This issue arises from the manner in which the objects are initialized.
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Analysis
by VulDB Data Team • 08/27/2025
The vulnerability identified as CVE-2023-26136 affects the tough-cookie package, specifically versions prior to 4.1.3, and represents a prototype pollution vulnerability that can have significant security implications for applications relying on cookie management. This flaw manifests when the CookieJar is configured to operate in rejectPublicSuffixes=false mode, creating a dangerous condition where attacker-controlled input can manipulate the prototype of JavaScript objects through improper cookie handling mechanisms.
The technical root cause of this vulnerability stems from inadequate object initialization practices within the cookie processing logic. When cookies are parsed and stored in the CookieJar, the package fails to properly validate or sanitize cookie attributes before incorporating them into the underlying object structure. This improper handling allows malicious cookie values to influence the prototype chain of objects, potentially enabling attackers to modify or inject properties into the Object.prototype. The vulnerability is particularly concerning because it occurs during the cookie parsing phase, which is a fundamental operation in web applications that process HTTP cookies.
The operational impact of this prototype pollution vulnerability extends beyond simple data corruption, as it can enable various attack vectors including but not limited to remote code execution, denial of service conditions, and privilege escalation within affected applications. When applications parse user-supplied cookie data without proper sanitization, an attacker can craft malicious cookie values that, when processed by the vulnerable tough-cookie package, pollute the prototype chain and potentially affect the application's behavior. This vulnerability aligns with CWE-471, which describes the weakness of "Modification of Assumed-Immutable Data" and can be mapped to ATT&CK technique T1190 for "Exploit Public-Facing Application" as it represents a vulnerability in a widely used npm package that applications may expose to external users.
Mitigation strategies for CVE-2023-26136 primarily involve upgrading the tough-cookie package to version 4.1.3 or later, which includes proper validation and sanitization of cookie attributes during the parsing process. Organizations should conduct comprehensive vulnerability assessments to identify all applications and services utilizing vulnerable versions of this package, particularly those that process external cookie data or expose cookie management functionality to untrusted users. Additionally, implementing proper input validation at multiple layers of the application architecture can provide defense-in-depth protection against similar vulnerabilities, while monitoring for unusual cookie parsing patterns may help detect potential exploitation attempts. The fix implemented in version 4.1.3 addresses the core issue by ensuring that cookie attributes are properly validated before being incorporated into object structures, preventing unauthorized modifications to prototype properties.