Spring Framework Vulnerability Enables RFD Attacks via “Content-Disposition” Header

A critical security vulnerability has been discovered in the popular Spring Framework that allows attackers to execute Reflected File Download (RFD) attacks through malicious manipulation of Content-Disposition headers.

The vulnerability, identified as CVE-2020-5398, affects multiple versions of Spring Framework and was responsibly disclosed by security researcher Jakob Linskeseder from the Dynatrace Security Team.

The security vulnerability impacts Spring Framework versions 6.0.x starting from 6.0.5, all versions in the 6.1.x series, and versions in the 6.2.x branch.

Specifically, the affected versions include Spring Framework 6.2.0 through 6.2.7, 6.1.0 through 6.1.20, and 6.0.5 through 6.0.28.

Notably, older unsupported versions of the framework remain unaffected by this particular vulnerability.

The vulnerability emerges when applications utilize Spring’s org.springframework.http.ContentDisposition class to prepare Content-Disposition headers with non-ASCII charset specifications.

This becomes particularly dangerous when the filename attribute within these headers is populated using data derived from user-supplied input without proper sanitization measures in place.

Spring Framework, being one of the most widely adopted Java application frameworks in enterprise environments, makes this vulnerability particularly concerning for organizations relying on web applications built with these affected versions.

The framework’s extensive use in commercial and open-source projects amplifies the potential impact across numerous systems worldwide.

Spring Framework Vulnerability

The RFD attack becomes possible when several specific conditions align simultaneously within vulnerable applications.

The attack vector requires that applications set Content-Disposition response headers using Spring’s ContentDisposition class, specifically through the ContentDisposition.Builder#filename(String, Charset) method where the charset parameter is non-ASCII.

For successful exploitation, attackers must be able to influence the filename value through user-supplied input that remains unsanitized by the application.

Additionally, the attacker must possess the capability to inject malicious commands into the downloaded content of the HTTP response, following methodologies outlined in established RFD attack research.

Applications remain protected against this vulnerability if they avoid setting Content-Disposition response headers entirely, use alternative methods for filename specification such as ContentDisposition.Builder#filename(String) or ContentDisposition.Builder#filename(String, ASCII), or implement proper input sanitization for user-supplied filename values.

Furthermore, applications that prevent attackers from injecting malicious content into response downloads maintain their security posture.

Mitigations

Spring Framework maintainers have released patched versions to address this security vulnerability across all affected branches.

Users running Spring Framework 6.2.x should upgrade to version 6.2.8, which is available through open-source channels. Similarly, applications using 6.1.x versions should migrate to 6.1.21, also available as an open-source release.

For organizations using Spring Framework 6.0.x versions, the fix is available in version 6.0.29, though this release is distributed through commercial channels only.

The development team emphasizes that no additional mitigation steps are necessary beyond upgrading to the corresponding fixed versions.

Security experts recommend immediate assessment of applications using the affected Spring Framework versions, particularly those handling file downloads with user-controlled filename parameters.

Organizations should prioritize updates based on their exposure to user-supplied input in Content-Disposition header construction and implement comprehensive input validation as a defense-in-depth strategy.

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