CVE-2015-7193 in Firefox
Summary
by MITRE
Mozilla Firefox before 42.0 and Firefox ESR 38.x before 38.4 improperly follow the CORS cross-origin request algorithm for the POST method in situations involving an unspecified Content-Type header manipulation, which allows remote attackers to bypass the Same Origin Policy by leveraging the lack of a preflight-request step.
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Analysis
by VulDB Data Team • 10/23/2024
This vulnerability affects mozilla firefox versions prior to 42.0 and firefox esr 38.x versions prior to 38.4, representing a critical security flaw in the browser's implementation of cross-origin resource sharing protocols. The issue stems from improper handling of cors cross-origin request algorithms specifically when processing post method requests with unspecified content-type headers. This flaw creates a significant bypass opportunity for remote attackers seeking to circumvent the same origin policy that forms a fundamental pillar of web security architecture.
The technical root cause lies in the browser's failure to properly execute the preflight request step when content-type headers are unspecified during post method requests. According to the cors specification and aligned with cwe-346 known as "improper constraint validation", firefox was not adequately validating the content-type header before allowing cross-origin requests to proceed. This oversight creates a scenario where attackers can manipulate the content-type header to unspecified values, effectively bypassing the security mechanisms that should enforce preflight requests for potentially dangerous cross-origin operations.
The operational impact of this vulnerability is severe as it allows remote attackers to perform cross-origin requests without proper authorization checks that should normally occur through preflight mechanisms. This means malicious actors can potentially access resources that should be restricted to same-origin requests, enabling data exfiltration, unauthorized api calls, and other cross-site scripting attacks. The vulnerability specifically affects scenarios where the content-type header is not explicitly set, creating an ambiguity that the browser fails to properly resolve through standard cors protocol enforcement.
This flaw aligns with attack techniques documented in the attack pattern taxonomy under patterns related to cross-site request forgery and privilege escalation through protocol manipulation. The vulnerability represents a failure in the browser's security model implementation and can be exploited to undermine the integrity of web applications that rely on cors for security boundaries. Security professionals should note that this issue demonstrates the critical importance of proper cors implementation, particularly in handling edge cases where header values are unspecified or ambiguous.
Organizations should immediately update to firefox versions 42.0 or later for regular releases and firefox esr 38.4 or later for extended support releases to mitigate this vulnerability. Additionally, network administrators should implement monitoring for unusual cross-origin request patterns and consider additional security layers such as content security policies and web application firewalls as defensive measures. The fix implemented by mozilla addressed the specific algorithmic oversight in cors handling, ensuring that proper preflight request steps are executed regardless of content-type header specification levels.