CVE-2020-13432 – This vulnerability in rejetto HFS (HTTP File Se... (How to Fix)

Q: What is the severity of CVE-2020-13432?

CVE-2020-13432 has a CVSS score of 7.5 (HIGH). This vulnerability in rejetto HFS (HTTP File Server) allows remote attackers to trigger a buffer overflow via concurrent HTTP requests with long URIs or headers when virtual files/folders are used. It affects HFS v2.3m Build #300, potentially causing denial of service or arbitrary code execution. Anyone running this specific version with virtual files/folders enabled is vulnerable.

📋 TL;DR

This vulnerability in rejetto HFS (HTTP File Server) allows remote attackers to trigger a buffer overflow via concurrent HTTP requests with long URIs or headers when virtual files/folders are used. It affects HFS v2.3m Build #300, potentially causing denial of service or arbitrary code execution. Anyone running this specific version with virtual files/folders enabled is vulnerable.

💻 Affected Systems

Products:

rejetto HFS (HTTP File Server)

Versions: v2.3m Build #300

Operating Systems: Windows, Linux, All platforms running HFS

Default Config Vulnerable: ⚠️ Yes

Notes: Requires virtual files or folders feature to be used

📦 What is this software?

Http File Server by Rejetto

View all CVEs affecting Http File Server →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise

🟠

Likely Case

Denial of service causing application crashes and service disruption

🟢

If Mitigated

Limited to denial of service if exploit fails to achieve code execution

🌐 Internet-Facing: HIGH - Remote unauthenticated exploitation possible

🏢 Internal Only: MEDIUM - Still exploitable but requires internal network access

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Public exploit code available, requires concurrent requests to trigger

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in commit b8ebfc4e22948e1a61506cd66e397b61ea5ea5de

Vendor Advisory: https://github.com/rejetto/hfs2/commit/b8ebfc4e22948e1a61506cd66e397b61ea5ea5de

Restart Required: Yes

Instructions:

1. Download latest HFS version from official repository 2. Replace existing installation 3. Restart HFS service

🔧 Temporary Workarounds

Disable virtual files/folders

all

Disable the virtual files and folders feature in HFS configuration

Edit hfs.ini and set virtual_folders=false

Implement request filtering

all

Use reverse proxy or WAF to filter long URIs and headers

Configure nginx/apache to limit request_line_size and large_client_header_buffers

🧯 If You Can't Patch

Isolate HFS server in separate network segment with strict firewall rules
Implement rate limiting to prevent concurrent exploitation attempts

🔍 How to Verify

Check if Vulnerable:

Check HFS version in web interface or about dialog, verify if running v2.3m Build #300

Check Version:

Check HFS web interface or examine hfs.exe properties on Windows

Verify Fix Applied:

Verify version is newer than v2.3m Build #300 or check for commit b8ebfc4e in installation

📡 Detection & Monitoring

Log Indicators:

Multiple concurrent requests with long URIs (>1024 chars)
Application crash logs
Access violation errors in Windows Event Log

Network Indicators:

HTTP requests with unusually long URIs or headers
Multiple concurrent connections to HFS port

SIEM Query:

source="hfs.log" AND (uri_length>1024 OR header_length>4096)

📊 Metadata

CVE ID: CVE-2020-13432

CVSS v3 Score: 7.5 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-120

Published: June 8, 2020

Last Updated: November 21, 2024

🔗 References

http://hyp3rlinx.altervista.org/advisories/HFS-HTTP-FILE-SERVER-v2.3-REMOTE-BUFFER-OVERFLOW-DoS.txt Exploit,Third Party Advisory
http://packetstormsecurity.com/files/157980/HFS-Http-File-Server-2.3m-Build-300-Buffer-Overflow.html Exploit,Third Party Advisory,VDB Entry
http://seclists.org/fulldisclosure/2020/Jun/13 Exploit,Mailing List,Third Party Advisory
http://seclists.org/fulldisclosure/2021/Apr/12
https://github.com/rejetto/hfs2/commit/b8ebfc4e22948e1a61506cd66e397b61ea5ea5de Patch,Third Party Advisory
https://packetstormsecurity.com/files/157980/HFS-Http-File-Server-2.3m-Build-300-Buffer-Overflow.html Exploit,Third Party Advisory,VDB Entry
https://www.rejetto.com/hfs/?f=wn Release Notes,Vendor Advisory
http://hyp3rlinx.altervista.org/advisories/HFS-HTTP-FILE-SERVER-v2.3-REMOTE-BUFFER-OVERFLOW-DoS.txt Exploit,Third Party Advisory
http://packetstormsecurity.com/files/157980/HFS-Http-File-Server-2.3m-Build-300-Buffer-Overflow.html Exploit,Third Party Advisory,VDB Entry
http://seclists.org/fulldisclosure/2020/Jun/13 Exploit,Mailing List,Third Party Advisory
http://seclists.org/fulldisclosure/2021/Apr/12
https://github.com/rejetto/hfs2/commit/b8ebfc4e22948e1a61506cd66e397b61ea5ea5de Patch,Third Party Advisory
https://packetstormsecurity.com/files/157980/HFS-Http-File-Server-2.3m-Build-300-Buffer-Overflow.html Exploit,Third Party Advisory,VDB Entry
https://www.rejetto.com/hfs/?f=wn Release Notes,Vendor Advisory

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