________________________________________________________________________ From the low-hanging-fruit-department F-SECURE Generic Malformed Container bypass (RAR) ________________________________________________________________________ Ref : [TZO-15-2020] - F-SECURE Generic Malformed Container bypass (RAR) Vendor : F-SECURE Status : Patched CVE : none provided Blog : https://blog.zoller.lu/p/tzo-15-2020-f-secure-generic-malformed.html Vulnerability Dislosure Policy: https://caravelahq.com/b/policy/20949 Affected Products ================= F-Secure Email and Server Security F-Secure Internet GateKeeper F-SECURE CLOUD PROTECTION FOR SALESFORCE Linux below 17.0.605.474 I. Background ---------------------------- Quote: "Unprecedented challenges threaten to undermine the very survival of society. Only unprecedented innovation can prevent irreversible disasters. This is only possible if we trust the technology that can bring us together. From our humble beginnings more than thirty years ago, F-Secure has grown into a reliable cyber security leader, earning the trust of organizations and people around the world." II. Description ---------------------------- The parsing engine supports the RAR Archive. The parsing engine can be bypassed by specifically manipulating a RAR archive. III. Impact ---------------------------- Impacts depends on the contextual use of the product and engine within the organisation of a customer. Gateway Products (Email, HTTP Proxy etc) may allow the file through unscanned and give it a clean bill of health. Server side AV software will not be able to discover any code or sample contained within this ISO file and it will not raise suspicion even if you know exactly what you are looking for (Which is for example great to hide your implants or Exfiltration/Pivot Server). There is a lot more to be said about this bug class, so rather than bore you with it in this advisory I provide a link to my 2009 blog post http://blog.zoller.lu/2009/04/case-for-av-bypassesevasions.html IV. Patch / Advisory ---------------------------- - For the unix version (IGK) the fix was released on 20th January with library version 17.0.605.474 - For Windows the version was already out in December 2019. There were also avira's fixes as well. "We can conclude that January 20th date, since that is when the final fixes went out to production." V. Disclosure timeline ---------------------------- NOV 20 2019 - Report DEC 20 2019 - Windows fixes released JAN 20 2010 - Linux fix relesased