CVE-2014-9720 in Tornado
Summary
by MITRE
Tornado before 3.2.2 sends arbitrary responses that contain a fixed CSRF token and may be sent with HTTP compression, which makes it easier for remote attackers to conduct a BREACH attack and determine this token via a series of crafted requests.
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Analysis
by VulDB Data Team • 04/27/2025
The vulnerability identified as CVE-2014-9720 affects the Tornado web framework version 3.2.1 and earlier, presenting a significant security risk through improper handling of Cross-Site Request Forgery protection mechanisms. This flaw stems from the framework's use of a fixed CSRF token that remains constant across multiple requests, creating predictable security elements that adversaries can exploit. The vulnerability becomes particularly dangerous when combined with HTTP compression, as it enables attackers to perform BREACH attacks more effectively by leveraging the predictable token structure and compression artifacts. The technical implementation involves Tornado's response handling mechanism where the fixed token is embedded in responses without proper randomization or entropy, making it susceptible to statistical analysis and pattern recognition techniques that characterize BREACH attacks.
The operational impact of this vulnerability extends beyond simple token exposure, as it fundamentally undermines the security model of CSRF protection within the Tornado framework. When combined with HTTP compression, the vulnerability creates a scenario where attackers can exploit the compression algorithm's behavior to infer the fixed token through a series of carefully crafted requests that exploit the compression ratio differences between various token values. This attack vector represents a sophisticated approach that leverages the intersection of two security weaknesses: the predictability of CSRF tokens and the compression side-channel that reveals information about the token content. The vulnerability aligns with CWE-310, which addresses cryptographic weakness, and specifically relates to improper randomization of security tokens. The attack methodology follows patterns consistent with ATT&CK technique T1566.001, which involves credential access through the exploitation of web application vulnerabilities.
Mitigation strategies for this vulnerability require immediate implementation of framework upgrades to version 3.2.2 or later, where the fixed token issue has been resolved through proper token generation mechanisms. Organizations should also implement additional security controls such as disabling HTTP compression for sensitive responses, implementing proper token randomization, and deploying web application firewalls that can detect and block BREACH attack patterns. The fix implemented in the patched version addresses the core issue by ensuring that CSRF tokens are generated with sufficient entropy and are not reused across multiple requests, thereby eliminating the predictable nature that made the vulnerability exploitable. Security teams must also conduct thorough assessments of their application's response handling mechanisms to ensure that no other predictable elements exist within HTTP responses that could be exploited in similar compression-based attacks. The vulnerability serves as a reminder of the importance of proper entropy in security token generation and the potential risks introduced by seemingly benign features like HTTP compression when combined with predictable security elements.