CVEs / CVE-2025-31161

CVE-2025-31161: CrushFTP Authentication Bypass Vulnerability

• Known exploited in the CISA KEV catalog since 7 Apr 2025
• critical 9.8 CVSS 3.1 (NVD)
• EPSS 99.9% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
• Last changed at its sources 17 Jun 2026

Summary

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.

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.

Affected and fixed versions

Exploitation

Severity

References

• CVE-2025-31161 on NVD
• CVE-2025-31161 in the CISA KEV catalog
• https://www.crushftp.com/crush11wiki/Wiki.jsp?page=Update (cited by CISA)
• 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