CVE-2025-31161
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedCrushFTP 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceCrushFTP versions 10 before 10.8.4 and 11 before 11.3.1 contain an authentication bypass vulnerability in the AWS4-HMAC (S3-compatible) HTTP authorization method. Attackers can exploit a race condition or send a mangled AWS4-HMAC header with just a username and trailing slash to trigger an anypass authentication process, bypassing normal credential verification. An index-out-of-bounds error from the malformed request stops session cleanup, allowing trivial authentication as any known user (including crushadmin) and full administrative compromise.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 10.0.0, < 10.8.4>= 11.0.0, < 11.3.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed CrushFTP versionAccess the CrushFTP admin interface and navigate to the 'About' or 'System Info' section, or check the version displayed on the login page. If using command line, check any startup logs or the installer metadata.Affected if The installed version is 10.0.0 through 10.8.3, or 11.0.0 through 11.3.0 (any version below 10.8.4 or 11.3.1).
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Verify if S3-compatible (AWS4-HMAC) API interface is enabledCheck the CrushFTP admin panel under 'Server' > 'Protocols' or 'Interface Settings' to see if the S3-compatible / WebDAV / API interface is enabled and accessible.Affected if The S3-compatible API interface is exposed and reachable from the network.
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Review authentication logs for mangled AWS4-HMAC headersExamine CrushFTP access and server logs for requests containing AWS4-HMAC authorization headers where the header value starts with the username followed by '/' (for example: 'Authorization: AWS4-HMAC username/...').Affected if Logs contain malformed AWS4-HMAC authorization attempts or unusual authentication patterns.
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Check for unexpected administrative sessionsIn the CrushFTP admin interface, review active sessions and user accounts, particularly looking for the 'crushadmin' account or any other administrative accounts that were not created by legitimate administrators.Affected if Unknown administrative accounts exist or administrative sessions are active that were not initiated by known administrators.
You are affected if your CrushFTP version is below 10.8.4 or 11.3.1 AND the S3-compatible API interface is enabled and reachable, especially if logs show suspicious AWS4-HMAC authentication patterns or unexpected administrative access.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped10.8.411.3.1
Immediately upgrade CrushFTP to version 10.8.4/11.3.1 or later. Review server logs for unauthorized access attempts since March 2025, reset all administrative credentials, and verify no unauthorized accounts or backdoors were created.
CrushFTP 10.8.4 or later for 10.x branch; CrushFTP 11.3.1 or later for 11.x branch
- Identify currently running CrushFTP version using admin interface or system inventory
- If running version 10.x (>= 10.0.0): Upgrade to CrushFTP version 10.8.4 or later
- If running version 11.x (>= 11.0.0): Upgrade to CrushFTP version 11.3.1 or later
- Download the appropriate installer from the official CrushFTP website (crushftp.com)
- Stop the CrushFTP service before upgrading
- Install the new version following standard CrushFTP upgrade procedures
- Restart the CrushFTP service after upgrade
- Verify the upgrade was successful by checking the version in the admin interface
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2025-31161 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-31161 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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