CVE-2005-4685 in Firefox
Summary
by MITRE
Firefox and Mozilla can associate a cookie with multiple domains when the DNS resolver has a non-root domain in its search list, which allows remote attackers to trick a user into accepting a cookie for a hostname formed via search-list expansion of the hostname entered by the user, or steal a cookie for an expanded hostname, as demonstrated by an attacker who operates an ap1.com Internet web site to steal cookies associated with an ap1.com.example.com intranet web site.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 05/02/2019
This vulnerability represents a critical cookie domain validation flaw in mozilla firefox and mozilla browser implementations that stems from improper handling of dns search lists during cookie domain assignment. The issue occurs when a dns resolver contains non-root domains in its search list configuration, creating a scenario where browser cookie management becomes susceptible to domain expansion attacks. The vulnerability exploits the fundamental trust relationship between browser cookie handling and domain validation mechanisms, allowing attackers to manipulate cookie scope through dns search list expansion techniques.
The technical flaw manifests when a user enters a hostname that matches a domain in the dns search list, causing the browser to expand the hostname using the search list entries. For instance when a user navigates to ap1.com, but the dns resolver has example.com in its search list, the browser may associate cookies with the expanded hostname ap1.com.example.com. This creates a security boundary violation where cookies intended for one domain can be accessed by another domain that shares a portion of the dns search list structure. The vulnerability specifically affects how browsers process cookie domain attributes when the hostname being accessed is subject to dns search list expansion, leading to improper cookie scope enforcement.
The operational impact of this vulnerability is significant as it enables sophisticated cross-domain cookie theft and manipulation attacks. Attackers can leverage this weakness to perform session hijacking by stealing cookies associated with internal network domains that users access through external web browsers. The attack vector demonstrates a real-world scenario where an attacker operating a legitimate website at ap1.com can steal cookies that would normally be restricted to internal domains like ap1.com.example.com. This creates a pathway for privilege escalation and unauthorized access to internal network resources that should remain protected by cookie security mechanisms.
The vulnerability aligns with multiple cybersecurity frameworks and threat models, particularly relating to common weakness enumeration cw310 which addresses improper cookie domain validation and attack techniques documented under attack technique t1185 for dns cache poisoning and t1566 for credential access through web application attacks. The flaw represents a classic case of insufficient input validation in network protocol implementations where the browser fails to properly validate the relationship between user-entered hostnames and the actual network resolution results obtained through dns search list expansion. This type of vulnerability is particularly dangerous in enterprise environments where internal dns structures often contain multiple subdomain levels that can be exploited through this cookie domain expansion mechanism.
Mitigation strategies should focus on implementing strict cookie domain validation that does not rely on dns search list expansion for determining cookie scope, enforcing proper hostname resolution validation, and ensuring that browser implementations properly distinguish between user-entered hostnames and expanded dns results. Organizations should also consider implementing dns resolver configurations that minimize the risk of search list expansion attacks, while browser vendors should enhance their cookie handling mechanisms to explicitly validate domain boundaries and prevent automatic cookie association with expanded hostnames that do not match the original user-entered domain. The vulnerability underscores the importance of proper security boundary enforcement in web browser implementations and the need for comprehensive testing of dns resolution behaviors in cookie management systems.