Skip to main content
Live Webinar with SANS (June 25)— Agentic CTI Automation for Fun & ProfitRegister Free
Mallory
HighPublic exploit

Authenticated arbitrary PHP file upload leading to RCE in Flatnux 2021-03.25

IdentifiersCVE-2023-53956CWE-434· Unrestricted Upload of File with…

Flatnux 2021-03.25 contains an authenticated file upload flaw in its file manager that permits administrative users to upload arbitrary PHP files. An attacker with admin credentials can place a malicious PHP script into the web root (or otherwise web-accessible) directory and then invoke it via HTTP, resulting in remote code execution in the context of the web server process.

Share:
For your environment

Are you exposed to this one?

Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.

ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Remote code execution on the Flatnux server by an authenticated attacker with administrative access. This can lead to full compromise of the application and underlying host depending on web server privileges, with high impact to confidentiality, integrity, and availability.

Mitigation

If you can’t patch tonight, do this now.

Restrict/disable PHP uploads via the file manager; enforce server-side allow-list validation (MIME and extension) and reject dangerous types; store uploads outside the web root and serve them via a non-executable handler; configure the web server/PHP to disallow script execution in upload directories (e.g., disable PHP engine / remove handler mappings); monitor for and remove unexpected PHP files in web-accessible paths.

Remediation

Patch, then assume compromise.

Update Flatnux to a fixed/newer version that corrects the file manager upload handling. Ensure the file manager enforces strict allow-listing of uploadable types and prevents placement of executable content into web-accessible directories.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
FlatnuxFlatnuxapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4

Community discussion across Reddit, Mastodon, and other social sources.