---
title: "CVE-2025-31161: CrushFTP Authentication Bypass Vulnerability"
url: https://erroneo.us/security/cve/CVE-2025-31161/
description: "CVE-2025-31161 (CrushFTP CrushFTP): Exploited in the wild (CISA KEV). CrushFTP 10 before 10.8.4 and 11 before 11.3.1 allows authentication bypass and…"
type: vulnerability-record
section: "Security Digest"
date_published: 2025-04-03
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-31161"
kev: true
cvss: 9.8
epss: 0.99966
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-31161: CrushFTP Authentication Bypass Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run CrushFTP CrushFTP. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-04-07, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-04-28 ; treat that as the outer limit, not the target. CISA also lists it as known to be used in ransomware campaigns .
- EPSS 100.0% , percentile 100.0: FIRST’s model estimates a 100.0% chance of exploitation activity in the next 30 days, higher than 100.0% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Check exposure. CrushFTP Auth Bypass CVE-2025-31161 Exploited in the Wild — Fixed since March 2025 and widely exploited from early April; if you run CrushFTP, make sure you are on a current build (later CrushFTP flaws raised the minimum) and audit for backdoor admin accounts.

## What it is

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 loginuserpass() 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.

## Affected products (CVE record)

- CrushFTP CrushFTP: 10 < 10.8.4, 11 < 11.3.1

## Severity

- mitre CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: added 2025-04-07; federal due date 2025-04-28. Known ransomware use: Known.
- CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 99.97% probability of exploitation activity in the next 30 days; percentile 100.0.

## Sources

- [Listed in CISA KEV notes (crushftp.com)](https://www.crushftp.com/crush11wiki/Wiki.jsp?page=Update)
- [CVE.org record CVE-2025-31161](https://www.cve.org/CVERecord?id=CVE-2025-31161)
- [NVD entry CVE-2025-31161](https://nvd.nist.gov/vuln/detail/CVE-2025-31161)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-31161)
- [outpost24.com](https://outpost24.com/blog/crushftp-auth-bypass-vulnerability/)
- [crushftp.com](https://crushftp.com/crush11wiki/Wiki.jsp?page=Update#section-Update-VulnerabilityInfo)
- [projectdiscovery.io](https://projectdiscovery.io/blog/crushftp-authentication-bypass)
- [darkreading.com](https://www.darkreading.com/vulnerabilities-threats/disclosure-drama-clouds-crushftp-vulnerability-exploitation)
- [huntress.com](https://www.huntress.com/blog/crushftp-cve-2025-31161-auth-bypass-and-post-exploitation)
- [attackerkb.com](https://attackerkb.com/topics/k0EgiL9Psz/cve-2025-2825/rapid7-analysis)
- [infosecurity-magazine.com](https://www.infosecurity-magazine.com/news/crushftp-flaw-exploited-disclosure/)
- [vicarius.io](https://www.vicarius.io/vsociety/posts/cve-2025-31161-detect-crushftp-vulnerability)
- [vicarius.io](https://www.vicarius.io/vsociety/posts/cve-2025-31161-mitigate-crushftp-vulnerability)

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Source page: https://erroneo.us/security/cve/CVE-2025-31161/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt