Date: Wed, 5 May 2021 09:39:22 -0700 From: Aaron Patterson <aaron.patterson@...il.com> To: ruby-security-ann@...glegroups.com, rubyonrails-security@...glegroups.com, oss-security@...ts.openwall.com Subject: [CVE-2021-22885] Possible Information Disclosure / Unintended Method Execution in Action Pack There is a possible information disclosure / unintended method execution vulnerability in Action Pack which has been assigned the CVE identifier CVE-2021-22885. Versions Affected: >= 2.0.0. Not affected: < 2.0.0. Fixed Versions: 18.104.22.168, 22.214.171.124, 126.96.36.199, 5.2.6 Impact ------ There is a possible information disclosure / unintended method execution vulnerability in Action Pack when using the `redirect_to` or `polymorphic_url` helper with untrusted user input. Vulnerable code will look like this: ``` redirect_to(params[:some_param]) ``` All users running an affected release should either upgrade or use one of the workarounds immediately. Releases -------- The FIXED releases are available at the normal locations. Workarounds ----------- To work around this problem, it is recommended to use an allow list for valid parameters passed from the user. For example: ``` private def check(param) case param when "valid" param else "/" end end def index redirect_to(check(params[:some_param])) end ``` Or force the user input to be cast to a string like this: ``` def index redirect_to(params[:some_param].to_s) end ``` Patches ------- To aid users who aren't able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset. * 5-2-information-disclosure.patch - Patch for 5.2 series * 6-0-information-disclosure.patch - Patch for 6.0 series * 6-1-information-disclosure.patch - Patch for 6.1 series Please note that only the 5.2, 6.0, and 6.1 series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases. Credits ------- Thanks to Benoit Côté-Jodoin from Shopify for reporting this. -- Aaron Patterson http://tenderlovemaking.com/ Content of type "text/html" skipped Download attachment "5-2-information-disclosure.patch" of type "application/octet-stream" (5732 bytes) Download attachment "6-1-information-disclosure.patch" of type "application/octet-stream" (5729 bytes) Download attachment "6-0-information-disclosure.patch" of type "application/octet-stream" (5729 bytes)
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