CVE-2020-13432: 
Rejetto HFS vulnerability analysis and mitigation

rejetto HFS (aka HTTP File Server) v2.3m Build #300, when virtual files or folders are used, allows remote attackers to trigger an invalid-pointer write access violation via concurrent HTTP requests with a long URI or long HTTP headers like Cookie, User-Agent etc. The vulnerability was discovered in May 2020 and assigned CVE-2020-13432. The issue affects HFS v2.3m Build #300 and requires at least one saved virtual file or folder to be present on the target system (Hyp3rlinx Advisory).

The vulnerability allows remote unauthenticated attackers to send concurrent HTTP requests using an incrementing or specific payload range of junk characters for values in the URL parameters or HTTP headers sent to the server. This results in an invalid pointer write access violation causing the hfs.exe server to crash. The issue was classified as 'EXPLOITABLE' according to Microsoft's !exploitable debugger extension, with the bug manifesting as a User Mode Write Access Violation (Hyp3rlinx Advisory).

Successful exploitation of this vulnerability results in a denial of service condition by crashing the HFS server process. The attack can be performed remotely by an unauthenticated attacker, making it particularly dangerous for exposed servers (Hyp3rlinx Advisory).

The vendor released version 2.4 on June 7, 2020, which addresses this vulnerability. Users are advised to upgrade to the latest version. Additionally, the vendor has now indicated that version 2.3-2.4 should not be used anymore due to security vulnerabilities, and users should migrate to version 3 which is not affected by this issue (Rejetto Website).