CVE-2020-5217

In Secure Headers (RubyGem secure_headers), a directive injection vulnerability is present in versions before 3.8.0, 5.1.0, and 6.2.0. If user-supplied input was passed into append/override_content_security_policy_directives, a semicolon could be injected leading to directive injection. This could be used to e.g. override a script-src directive. Duplicate directives are ignored and the first one wins. The directives in secure_headers are sorted alphabetically so they pretty much all come before script-src. A previously undefined directive would receive a value even if SecureHeaders::OPT_OUT was supplied. The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning when this happens. This will result in innocuous browser console messages if being exploited/accidentally used. In future releases, we will raise application errors resulting in 500s. Depending on what major version you are using, the fixed versions are 6.2.0, 5.1.0, 3.8.0.

In Secure Headers (RubyGem secure_headers), a directive injection vulnerability is present in versions before 3.8.0, 5.1.0, and 6.2.0. If user-supplied input was passed into append/override_content_security_policy_directives, a semicolon could be injected leading to directive injection. This could be used to e.g. override a script-src directive. Duplicate directives are ignored and the first one wins. The directives in secure_headers are sorted alphabetically so they pretty much all come before script-src. A previously undefined directive would receive a value even if SecureHeaders::OPT_OUT was supplied. The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning when this happens. This will result in innocuous browser console messages if being exploited/accidentally used. In future releases, we will raise application errors resulting in 500s. Depending on what major version you are using, the fixed versions are 6.2.0, 5.1.0, 3.8.0.

### Impact If user-supplied input was passed into `append/override_content_security_policy_directives`, a semicolon could be injected leading to directive injection. This could be used to e.g. override a `script-src` directive. Duplicate directives are ignored and the first one wins. The directives in `secure_headers` are sorted alphabetically so they pretty much all come before `script-src`. A previously undefined directive would receive a value even if `SecureHeaders::OPT_OUT` was supplied. The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning when this happens. This will result in innocuous browser console messages if being exploited/accidentally used. In future releases, we will raise application errors resulting in 500s. > Duplicate script-src directives detected. All but the first instance will be ignored. See https://www.w3.org/TR/CSP3/#parse-serialized-policy > Note: In this case, the user agent SHOULD notify developers that a duplicate directive was ignored. A console warning might be appropriate, for example. ### Patches Depending on what major version you are using, the fixed versions are 6.2.0, 5.1.0, 3.8.0. ### Workarounds If you are passing user input into the above methods, you could filter out the input: ```ruby override_content_security_policy_directives(:frame_src, [user_input.gsub(";", " ")]) ``` ### References Reported in https://github.com/twitter/secure_headers/issues/418 https://www.w3.org/TR/CSP3/#parse-serialized-policy ### 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/issues/new) * DM @ndm on twitter

### Impact If user-supplied input was passed into `append/override_content_security_policy_directives`, a semicolon could be injected leading to directive injection. This could be used to e.g. override a `script-src` directive. Duplicate directives are ignored and the first one wins. The directives in `secure_headers` are sorted alphabetically so they pretty much all come before `script-src`. A previously undefined directive would receive a value even if `SecureHeaders::OPT_OUT` was supplied. The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning when this happens. This will result in innocuous browser console messages if being exploited/accidentally used. In future releases, we will raise application errors resulting in 500s. > Duplicate script-src directives detected. All but the first instance will be ignored. See https://www.w3.org/TR/CSP3/#parse-serialized-policy > Note: In this case, the user agent SHOULD notify developers that a duplicate directive was ignored. A console warning might be appropriate, for example. ### Patches Depending on what major version you are using, the fixed versions are 6.2.0, 5.1.0, 3.8.0. ### Workarounds If you are passing user input into the above methods, you could filter out the input: ```ruby override_content_security_policy_directives(:frame_src, [user_input.gsub(";", " ")]) ``` ### References Reported in https://github.com/twitter/secure_headers/issues/418 https://www.w3.org/TR/CSP3/#parse-serialized-policy ### 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/issues/new) * DM @ndm on twitter

En Secure Headers (secure_headers de RubyGem), una vulnerabilidad de inyección de directiva está presente en las versiones anteriores a 3.8.0, 5.1.0 y 6.2.0. Si una entrada suministrada por el usuario fue pasada a append/override_content_security_policy_directives, se podría inyectar un punto y coma conllevando a una inyección de directiva. Esto podría ser usado para, por ejemplo anular una directiva script-src. Las directivas duplicadas son ignoradas y la primera gana. Las directivas en secure_headers están ordenadas alfabéticamente, por lo que casi todas van antes de script-src. Una directiva previamente indefinida recibiría un valor inclusive si la función SecureHeaders::OPT_OUT fue suministrada. Las versiones corregidas convertirán silenciosamente los puntos y comas en espacios y emitirán una advertencia de desaprobación cuando esto suceda. Esto resultará en mensajes inocuos de la consola del navegador si está siendo explotada o usada accidentalmente. En futuras versiones, generaremos errores de aplicación resultando en 500. Según la versión principal que esté usando, las versiones corregidas son 6.2.0, 5.1.0, 3.8.0.