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CVE-2025-31161 — CrushFTP 10 before 10.8.4 and 11 before 11.3.1 allows authentication bypass and takeover…

Key facts

CVE-2025-31161 is a Critical (9.8) vulnerability: CrushFTP 10 before 10.8.4 and 11 before 11.3.1 allows authentication bypass and takeover…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-04-07), confirming active exploitation in the wild, and is linked to known ransomware campaigns.

Actively exploited — on the CISA KEV catalog

CVE-2025-31161 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-04-07), confirming exploitation in the wild. It is linked to known ransomware campaigns. Federal remediation deadline: 2025-04-28. Prioritise patching and deploy the detection and prevention rules below.
CVE CVE-2025-31161
Severity Critical (9.8)
CISA KEV Actively exploited (added 2025-04-07) · ransomware
Detection / prevention —
PoC poc.py
Source 2025/CVE-2025-31161/

Details

English | 한국어

Description

CrushFTP 10 before 10.8.4 and 11 before 11.3.1 allows authentication bypass and takeover of the crushadmin account (unless a DMZ proxy instance is used), as exploited in the wild in March and April 2025, aka "Unauthenticated HTTP(S) port access." A race condition exists in the AWS4-HMAC (compatible with S3) authorization method of the HTTP component of the FTP server. The server first verifies the existence of the user by performing a call to login_user_pass() with no password requirement. This will authenticate the session through the HMAC verification process and up until the server checks for user verification once more. The vulnerability can be further stabilized, eliminating the need for successfully triggering a race condition, by sending a mangled AWS4-HMAC header. By providing only the username and a following slash (/), the server will successfully find a username, which triggers the successful anypass authentication process, but the server will fail to find the expected SignedHeaders entry, resulting in an index-out-of-bounds error that stops the code from reaching the session cleanup. Together, these issues make it trivial to authenticate as any known or guessable user (e.g., crushadmin), and can lead to a full compromise of the system by obtaining an administrative account.

Vulnerability Details

Property Value
CVE ID CVE-2025-31161
CVSS Score 9.8

Proof of Concept

Download

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2025/CVE-2025-31161/poc.py

Usage

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start

# Clone and navigate to CVE directory
cd CVE-2025-31161

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints

Application URL Status
Vulnerable App http://localhost:8080 Shows vulnerability
Patched App http://localhost:8081 Demonstrates fix

Directory Structure

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References

  • https://crushftp.com/crush11wiki/Wiki.jsp?page=Update#section-Update-VulnerabilityInfo
  • https://outpost24.com/blog/crushftp-auth-bypass-vulnerability/
  • https://attackerkb.com/topics/k0EgiL9Psz/cve-2025-2825/rapid7-analysis
  • https://projectdiscovery.io/blog/crushftp-authentication-bypass
  • https://www.darkreading.com/vulnerabilities-threats/disclosure-drama-clouds-crushftp-vulnerability-exploitation
  • https://www.huntress.com/blog/crushftp-cve-2025-31161-auth-bypass-and-post-exploitation
  • https://www.infosecurity-magazine.com/news/crushftp-flaw-exploited-disclosure/
  • https://www.vicarius.io/vsociety/posts/cve-2025-31161-detect-crushftp-vulnerability
  • https://www.vicarius.io/vsociety/posts/cve-2025-31161-mitigate-crushftp-vulnerability
  • https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-31161

Generated by PoC Generator on 2026-06-24T10:07:12.394606142

Frequently asked questions

What is CVE-2025-31161?

CVE-2025-31161 is a Critical (9.8) vulnerability: CrushFTP 10 before 10.8.4 and 11 before 11.3.1 allows authentication bypass and takeover…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-04-07), confirming active exploitation in the wild, and is linked to known ransomware campaigns.

How do I detect CVE-2025-31161?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2025-31161?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

Is CVE-2025-31161 actively exploited?

Yes. CVE-2025-31161 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2025-04-07, which means it has been exploited in the wild. CISA also links it to known ransomware campaigns. CISA set a federal remediation deadline of 2025-04-28. Prioritise patching and deploy the detection and prevention rules above.

For authorized security testing and research only. See the full source and NVD record.