CVE-2023-5723 in Firefox
Summary
by MITRE • 10/25/2023
An attacker with temporary script access to a site could have set a cookie containing invalid characters using `document.cookie` that could have led to unknown errors. This vulnerability affects Firefox < 119.
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Analysis
by VulDB Data Team • 11/15/2023
The vulnerability identified as CVE-2023-5723 represents a significant security flaw in Mozilla Firefox browsers prior to version 119, specifically within the cookie handling mechanism. This issue stems from insufficient validation of cookie values when scripts attempt to set cookies through the document.cookie API interface. The flaw allows malicious actors with temporary script execution privileges on a target website to manipulate cookie values with invalid characters, potentially leading to unpredictable behavior within the browser's cookie management system. The vulnerability is particularly concerning because it leverages legitimate browser scripting capabilities to create malformed cookie data that could trigger unexpected errors or system instability.
The technical implementation of this vulnerability resides in Firefox's cookie parsing and validation logic within the web browser's JavaScript engine. When scripts execute document.cookie assignments, the browser should validate that cookie values conform to established standards and specifications. However, in affected versions, the validation process fails to properly sanitize cookie values containing characters that are outside the accepted cookie value ranges. This weakness creates an attack surface where malicious scripts can inject invalid cookie data that may cause the browser to crash, behave unpredictably, or potentially expose internal state information. The flaw operates at the intersection of web security boundaries where user-supplied script content interfaces with browser core functionality, making it particularly dangerous in environments where third-party scripts are executed.
The operational impact of CVE-2023-5723 extends beyond simple browser instability, as it could enable more sophisticated attacks when combined with other vulnerabilities or attack vectors. An attacker who gains temporary script access through cross-site scripting or similar techniques could exploit this flaw to cause persistent browser disruptions, potentially leading to session hijacking or credential theft if the malformed cookie data interacts with other vulnerable components. The vulnerability affects the integrity of the browser's cookie management system and could provide attackers with information disclosure opportunities, as error conditions might reveal internal browser state or memory contents. This issue particularly impacts web applications that rely heavily on cookie-based authentication and session management, as the instability could be leveraged to disrupt legitimate user sessions or create persistent access points for further exploitation.
Security practitioners should prioritize updating affected Firefox installations to version 119 or later, where the cookie validation logic has been enhanced to properly sanitize input values. Organizations should implement additional monitoring for unusual cookie-related errors or browser crashes that might indicate exploitation attempts. The vulnerability aligns with CWE-113, which addresses improper neutralization of characters or elements, and could potentially be leveraged as part of broader attack chains that map to ATT&CK techniques such as T1059 for execution and T1566 for social engineering. Network administrators should consider implementing web application firewalls that can detect and block suspicious cookie value patterns, while developers should ensure their applications properly validate cookie data even when operating within secure browser environments. The remediation process should include comprehensive testing of cookie handling mechanisms across all browser versions to ensure that similar vulnerabilities do not exist in other components of the web application stack.