CVE-2023-4055 in Firefox
Summary
by MITRE • 08/01/2023
When the number of cookies per domain was exceeded in `document.cookie`, the actual cookie jar sent to the host was no longer consistent with expected cookie jar state. This could have caused requests to be sent with some cookies missing. This vulnerability affects Firefox < 116, Firefox ESR < 102.14, and Firefox ESR < 115.1.
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Analysis
by VulDB Data Team • 06/20/2025
This vulnerability represents a critical inconsistency in Firefox's cookie handling mechanism that stems from improper management of cookie limits per domain. The issue manifests when the maximum number of cookies allowed for a specific domain is exceeded, causing Firefox to send an inconsistent cookie jar to the web host. This inconsistency occurs because the browser's internal cookie storage does not properly synchronize with what gets transmitted during HTTP requests, leading to a state where the actual cookies sent differ from the expected cookie state. The vulnerability affects multiple Firefox versions including Firefox 115 and earlier, Firefox ESR 102.13 and earlier, and Firefox ESR 115.0 and earlier, highlighting its widespread impact across different release channels and support cycles.
The technical flaw resides in Firefox's cookie management system where the browser fails to maintain proper state consistency when cookie limits are exceeded. This creates a scenario where the cookie jar stored in memory becomes desynchronized from the cookie jar that gets serialized and sent with HTTP requests. When the cookie limit per domain is reached, the browser's logic for determining which cookies to include in outgoing requests becomes unreliable, potentially omitting cookies that should be present. The inconsistency in cookie transmission can be attributed to improper cookie eviction algorithms or flawed state management during cookie overflow conditions, which directly violates fundamental principles of web security and session management. This type of vulnerability falls under the category of cookie injection or cookie manipulation issues that can lead to session hijacking or authentication bypass scenarios.
The operational impact of this vulnerability extends beyond simple cookie omission and can compromise user sessions, authentication states, and application security. When cookies are missing from requests, web applications may not recognize users as authenticated, leading to forced logouts or failed authentication attempts. More critically, if session cookies or authentication tokens are among the missing cookies, attackers could potentially exploit this inconsistency to hijack user sessions or gain unauthorized access to protected resources. The vulnerability creates a window where applications may behave inconsistently depending on whether the cookie jar state matches expectations, potentially allowing for credential leakage or privilege escalation. This issue particularly affects web applications that rely heavily on cookie-based authentication and session management, making it a significant concern for enterprise environments and applications handling sensitive data.
Mitigation strategies for this vulnerability should focus on immediate version upgrades to patched Firefox releases, specifically Firefox 116, Firefox ESR 102.14, and Firefox ESR 115.1, which contain the necessary fixes for cookie handling consistency. Organizations should also implement monitoring solutions to detect unusual cookie behavior patterns in their web applications, as this vulnerability could manifest as intermittent authentication failures or session management issues. Network security teams should consider implementing cookie integrity checks in their web application firewalls to identify and block requests with inconsistent cookie states. Additionally, developers should ensure their applications do not rely solely on cookie presence for critical security decisions and should implement redundant authentication mechanisms. The vulnerability aligns with CWE-200 (Information Exposure) and CWE-345 (Insufficient Verification of Data Authenticity) categories, and could be exploited through ATT&CK techniques involving credential access and session hijacking. Regular security audits of cookie handling mechanisms and implementation of proper cookie management practices should be prioritized to prevent similar issues in custom web applications and browser extensions.