CVE-2025-31161: CrushFTP Authentication Bypass Vulnerability

CISA Known Exploited Vulnerabilities

Name

CrushFTP Authentication Bypass Vulnerability

Vendor

CrushFTP

Product

CrushFTP

Added to the catalog

2025-04-07

Due date for US federal agencies

2025-04-28

Weaknesses

CWE-305

Catalog version

2026.10.30

CrushFTP contains an authentication bypass vulnerability in the HTTP authorization header that allows a remote unauthenticated attacker to authenticate to any known or guessable user account (e.g., crushadmin), potentially leading to a full compromise.

Required action (CISA)

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Ransomware use: CISA marks this vulnerability as known to be used in ransomware campaigns. CISA does not say which group used it.

Links in CISA's notes

• https://www.crushftp.com/crush11wiki/Wiki.jsp?page=Update
• https://nvd.nist.gov/vuln/detail/CVE-2025-31161

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2025-04-03T20:15:25.373

Last modified

2026-06-17T09:09:56.440

Weaknesses

CWE-305, NVD-CWE-Other

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.

References

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

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:42:22.836Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2025-31161

CVE record

Assigner

mitre

State

PUBLISHED

Published

2025-04-03T00:00:00.000Z

Updated

2025-10-21T22:55:22.326Z

Problem types

CWE-305 Authentication Bypass by Primary Weakness

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.

References

• https://outpost24.com/blog/crushftp-auth-bypass-vulnerability/
• https://crushftp.com/crush11wiki/Wiki.jsp?page=Update#section-Update-VulnerabilityInfo

Read on 2026-11-03T02:15:59.716Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2025/31xxx/CVE-2025-31161.json

Detection rules (SigmaHQ)

SigmaHQ rules whose own tags name this CVE. Each rule page shows the rule as its author published it.

• Suspicious CrushFTP Child Process (status experimental, level medium)

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/