CrushFTP VFS Sandbox Escape
CVE-2024-4040 is a critical-severity improper control of generation of code vulnerability in CrushFTP, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 10.7.1, 11.1.0 as the first without the flaw, so updating CrushFTP to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on April 24, 2024, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update CrushFTP to 10.7.1 or 11.1.0, whichever matches your release line, or a later version.
- CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Read the advisory on crushftp.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| CrushFTP | CrushFTP | 10.0 up to, but not including, 10.7.1; 11.0 up to, but not including, 11.1.0 | 10.7.1, 11.1.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA |
| CVSS 3.1 | 10.0 | Critical | NVD |
Official description
A server side template injection vulnerability in CrushFTP in all versions before 10.7.1 and 11.1.0 on all platforms allows unauthenticated remote attackers to read files from the filesystem outside of the VFS Sandbox, bypass authentication to gain administrative access, and perform remote code execution on the server.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Control of Generation of Code
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
How developers prevent this class of flaw
- Refactor your program so that you do not have to dynamically generate code.
- Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
More Improper Control of Generation of Code vulnerabilities (CWE-94)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Third-party and government advisories
- bleepingcomputer.com/news/security/crushftp-warns-users-to-patch-exploited-zero-day-immediately/Press/Media Coverage, Third Party Advisory
- rapid7.com/blog/post/2024/04/23/etr-unauthenticated-crushftp-zero-day-enables-complete-server-compromise/Third Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-4040US Government Resource
Technical write-ups (may include proof of concept)
- github.com/airbus-cert/CVE-2024-4040Exploit, Third Party Advisory
- reddit.com/r/crowdstrike/comments/1c88788/situational_awareness_20240419_crushftp_virtual/Exploit, Issue Tracking
Other vulnerabilities in CrushFTP
- 9.8 Critical severity
CrushFTP Unprotected Alternate Channel Exploited
- 9.8 Critical severity
CrushFTP Authentication Bypass Exploited
- 9.6 Critical severity
Recent Improper Control of Generation of Code vulnerabilities
- 7.8 High severity
- 8.8 High severity
- 9.8 Critical severity
- 10.0 Critical severity
- 9.8 Critical severity
- 8.1 High severity
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