CVE-2025-53119

Executive Summary

CVE-2025-53119 is an unauthenticated unrestricted file upload vulnerability that permits a remote, unauthenticated attacker to upload malicious binaries and scripts to the affected server. The vendor and product remain unidentified (UNKNOWN) at the time of reporting, and no CVSS vector details are publicly available; however, a base score of 7.5 (High) has been associated with this issue. The core impact is full compromise of the upload functionality, leading to arbitrary code execution, potential persistence, and lateral movement within the enterprise network where the vulnerable service is hosted. No independent patch verification exists (Patch Confidence: 2/4 — CLAIMED), and no CISA KEV listing or public exploit evidence has been confirmed.

Technical Analysis

The vulnerability exists within an unidentified web application or service that exposes an unrestricted file upload endpoint. The term "unrestricted" indicates that the application fails to implement adequate validation on the file type, file extension, MIME type, file size, or content disposition of uploaded files. This class of flaw aligns with CWE-434 ("Unrestricted Upload of File with Dangerous Type") in standard CWE taxonomy, although the CNA has not formally assigned a CWE identifier at this time.

From a code-level perspective, the vulnerable component likely processes HTTP multipart/form-data requests without sanitizing the filename parameter or inspecting the uploaded file's content beyond basic content-type heuristics. A typical flawed implementation would resemble the following pseudo-code:

// Vulnerable pattern: only checks MIME type, which is attacker-controlled
if ($_FILES['file']['type'] == 'image/png') {
    move_uploaded_file($_FILES['file']['tmp_name'], '/var/www/uploads/' . $_FILES['file']['name']);
}

Here, the MIME type is derived from the client-supplied HTTP header (Content-Type within the multipart body) and can be trivially forged by an attacker. Alternatively, the application may not check at all, simply moving the uploaded file to a web-accessible directory or executing it inline. The attack surface is the public-facing upload endpoint, which can be a file manager, profile picture uploader, document submission portal, or any other file-accepting functionality.

Additional contributing factors that amplify the severity include: (1) lack of random or sanitized filenames, meaning the attacker can control the exact file name (e.g., shell.php, run.jsp, evil.exe); (2) storage inside the web server document root, allowing direct HTTP access to the uploaded payload; (3) absence of double extension, content magic-byte, or decompression-bomb checks; and (4) no authentication or session validation prior to the upload, as indicated by the "unauthenticated" descriptor in the vulnerability summary. The OSV package information is marked N/A, suggesting that this is not a library or package dependency issue but rather an application-level misconfiguration or coding defect. The exploit chain is remote, network-based, and requires no prior user interaction.

Exploitation Scenarios

Because no public PoC or Nuclei template is confirmed for CVE-2025-53119, the following describes the generic-but-concrete technique an attacker would use against such an unrestricted upload flaw, adapted to THIS CVE's characteristics (unauthenticated, remote, web-based).

Step 1 — Reconnaissance / Target Identification
The attacker first discovers the vulnerable upload endpoint. With no vendor information, they likely rely on Shodan/Censys searches for web applications that expose file-upload forms without authentication. They look for HTTP responses containing <input type="file"> within forms that do not redirect to a login page. They may also probe directory listings (e.g., /uploads/, /files/, /images/) to confirm whether uploaded files are subsequently served back to clients. The attacker fingerprints the Web server version and scripting engine (e.g., Apache + PHP, Nginx + .NET) to tailor the payload.

Step 2 — Trigger / Weaponization
The attacker crafts a multipart HTTP POST request to the upload endpoint. The request includes a payload file with an executable extension. For a PHP target:

POST /upload.php HTTP/1.1
Host: target.victim.com
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryXyZ
Content-Length: 345

------WebKitFormBoundaryXyZ
Content-Disposition: form-data; name="file"; filename="backdoor.php"
Content-Type: image/jpeg

<?php system($_GET['c']); ?>
------WebKitFormBoundaryXyZ--

The filename is set to backdoor.php (server-side, not client-side) to overwrite or create a new PHP file in the uploads directory. The Content-Type is spoofed as image/jpeg to bypass naive MIME checks. For a .NET/IIS target, they might upload cmd.aspx with an embedded web shell. For Windows servers allowing executable upload, a binary .exe payload is used for direct execution or scheduled-task persistence.

Step 3 — Payload / Execution
Assuming the application stores the file in a web-accessible path (e.g., /var/www/html/uploads/backdoor.php), the attacker sends a second HTTP GET request to https://target.victim.com/uploads/backdoor.php?c=id to trigger execution. The PHP interpreter executes the injected code, returning the output of the id command in the HTTP response body. If the file is stored outside the document root, the attacker must use a secondary vulnerability (directory traversal or local file inclusion) to execute it; for the purposes of this CVE, the unrestricted nature implies direct reachability.

Step 4 — Post-Exploitation Impact
With code execution as the web server user (typically www-data, svc_app, or NETWORK SERVICE), the attacker performs the following:

• Persistence: A second web shell is hidden in a less-scanned directory (e.g., /img/.cache.php), and a cron job is added (if write permissions permit) to re-plant the shell after resets.
• Lateral Movement: The attacker reads configuration files (wp-config.php, .env, web.config) to extract database credentials, API keys, and cloud secrets.
• Privilege Escalation: Kernel exploits or SUID misuse are evaluated; if the server runs a vulnerable service (e.g., sudo misconfiguration), root or SYSTEM is obtained.
• Data Exfiltration: The attacker archives the file system, database dumps, and user data, then exfiltrates via HTTPS or DNS tunneling to a staging server.

Impact Assessment

The CVSS base score of 7.5 reflects a high-severity issue, though the breakdown (AV/AC/PR/UI/S/C/I/A) is unknown due to the missing vector string. In a likely network-adjacent or network-based attack vector with no privileges or user interaction, the confidentiality, integrity, and availability impacts are all rated high. The business impact is severe: an attacker gains the ability to compromise the application server, which often holds sensitive corporate data (customer PII, financial records, intellectual property). Because the vulnerability is unauthenticated, any internet-exposed instance is directly exploitable without credential guessing or phishing, making mass exploitation campaigns a realistic concern once proof-of-concept code surfaces.

The blast radius includes:

• Application Server: Full control over the web service process, enabling defacement, malware hosting, or crypto mining.
• Backend Database: If web application credentials are stolen, the attacker can read, modify, or delete all records.
• Adjacent Infrastructure: The compromised server becomes a pivot point for internal network scans and attacks against other enterprise assets.
• Supply Chain: If the vulnerable application is a third-party appliance or SaaS component, downstream tenants may be affected.

No CISA KEV entry exists, meaning the vulnerability is not yet known to be exploited in the wild according to CISA’s catalog; however, unrestricted upload flaws are among the most commonly chained exploits (e.g., CVE-2021-41773, CVE-2019-16113), and their historical adoption rate by ransomware groups and APTs is high.

Detection Guidance

Sigma Rule

The following Sigma rule detects HTTP responses containing common web shell markers following a file-upload POST request, suitable for proxy or web server log monitoring.

title: CVE-2025-53119 Unrestricted File Upload - Web Shell Access
id: 4f6a2b8e-7c5d-4e1a-9f3b-2d8c4a6e1f00
status: experimental
description: Detects HTTP GET requests to uploaded web shells after a POST to an upload endpoint, indicating potential exploitation.
author: Valtersit TH-Intel Team
logsource:
    category: webserver
    product: generic
detection:
    selection_post:
        cs-method: 'POST'
        cs-uri-query|contains:
            - 'upload'
            - 'file_upload'
            - 'do_upload'
    selection_get:
        cs-method: 'GET'
        cs-uri-query|contains:
            - '.php?c='
            - '.jsp?cmd='
            - '.aspx?cmd='
            - 'eval('
            - 'system('
    selection_common:
        cs-uri-path|endswith:
            - '.php'
            - '.jsp'
            - '.aspx'
            - '.exe'
    condition: selection_post and selection_get and selection_common
    timeframe: 10m
falsepositives:
    - Legitimate admins uploading and immediately downloading files with query strings (rare)
level: high

YARA Rule

This YARA rule scans files or memory captures for typical web shell markers that would be uploaded using this vulnerability.

rule CVE_2025_53119_Unrestricted_Upload_Webshell
{
    meta:
        author = "Valtersit TH-Intel Team"
        description = "Detects web shell payloads commonly uploaded via unrestricted file upload vulnerabilities"
        cve = "CVE-2025-53119"
        date = "2025-05-15"
    strings:
        $php_system = /<\?php\s*(system|shell_exec|passthru)\s*\(/ ascii nocase
        $php_eval = /<\?php\s*eval\s*\(/ ascii nocase
        $asp_cmd = /<%\s*execute\(/ ascii nocase
        $jsp_cmd = /Runtime\.getRuntime\(\)\.exec/ ascii nocase
        $powershell = /powershell\s+(-enc|-e|-command)/ ascii nocase
        $file_upload = /Content-Disposition:\s*form-data;\s*name=".*file"/ ascii nocase
        $executable_ext = /\.(php|jsp|aspx|exe|sh|pl|py)\r?\n/ ascii nocase
    condition:
        ( uint16(0) == 0x5A4D or file_extension matches /\.(php|jsp|aspx|exe|sh|pl|py)$/ ) and
        ( 2 of ($php_*) or $asp_cmd or $jsp_cmd or $powershell ) and
        ( $file_upload or $executable_ext )
}

Suricata IDS Rule

Network-level rule protecting the upload endpoint and detecting post-exploitation web shell access.

alert http any any -> any any (msg:"CVE-2025-53119 Unrestricted File Upload - Web Shell Execution Attempt"; flow:established,to_server; content:"POST"; http_method; content:"upload"; http_uri; nocase; content:".php"; http_uri; nocase; content:"filename="; http_client_body; pcre:"/filename=\"[^"]+\.(php|jsp|aspx|exe|sh|pl|py)\"/iR"; classtype:attempted-admin; sid:20255311; rev:1;)

Elastic Detection

EQL query to surface upload events immediately followed by execution or suspicious file creation within a short window.

sequence by host.name with maxspan=60s
  [ file where event.action == "write" and file.extension in ("php", "jsp", "aspx", "exe", "sh", "py") and
    process.name != null and process.name in ("httpd", "apache2", "nginx", "w3wp.exe") ]
  [ process where event.action == "exec" and process.parent.name in ("httpd", "apache2", "nginx", "w3wp.exe") and
    process.args : ("*id*", "*whoami*", "*cmd*", "*powershell*") ]

Splunk SPL Query

Search IIS/Apache access logs for suspicious upload-plus-execute patterns.

index=web sourcetype=access_combined
| eval upload_flag = if(method=="POST" AND uri_path LIKE "%upload%", 1, 0)
| eval shell_flag = if(method=="GET" AND (uri_path LIKE "%.php%" OR uri_path LIKE "%.jsp%" OR uri_path LIKE "%.aspx%") AND uri_query LIKE "%c=%", 1, 0)
| stats sum(upload_flag) as uploads, sum(shell_flag) as shell_requests by clientip, host
| where uploads > 0 AND shell_requests > 0
| table _time, clientip, host, uploads, shell_requests

Wazuh OSSEC Rule

XML rule for Wazuh that flags web server error logs showing file uploads with dangerous extensions.

<group name="web,upload,vulnerability,">
  <rule id="100253" level="12">
    <decoded_as>json</decoded_as>
    <field name="url">\.(php|jsp|aspx|exe|sh|pl|py)$</field>
    <field name="method">POST</field>
    <description>CVE-2025-53119: Unrestricted file upload attempt with executable extension.</description>
    <group>upload_attack,</group>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence is 2/4 (CLAIMED — single source claims patch (not independently confirmed)). The vendor has not been identified, and no CVE-affected version list or patch source is available. Until the vendor is published, treat the product as unpatched.

1. Immediate Mitigations (stop bleeding):

   • Disable or restrict access to the upload endpoint at the perimeter: apply WAF rules to block any HTTP POST requests to upload paths containing executable file extensions (.php, .jsp, .aspx, .exe, etc.).
   • Move the upload storage directory outside the web root and configure the application to serve uploaded files via a separate internal handler that streams content with forced Content-Disposition: attachment.
   • Scan all existing upload directories for unexpected executable files; remove any suspicious files and investigate their origin.
   • Require authentication for the upload functionality regardless of application design, if possible.

2. Patch/Upgrade Steps:

   • Monitor vendor advisory feeds (NVD, vendor security pages) for the CVE-2025-53119 update; the CNA name is UNKNOWN, but NVD will publish the responsible vendor when disclosed.
   • Once a vendor is identified, upgrade to the patched version or apply the released hotfix. Validate the patch hash and test in a staging environment first.
   • If the product is custom-developed, implement code-level fixes: (a) validate file extension against a strict whitelist; (b) require and verify actual file magic bytes (e.g., using finfo or getimagesize); (c) generate random file names (e.g., UUID) and never accept user-supplied names; (d) restrict file size to a configurable maximum; (e) ensure the upload directory has no execute permissions (chmod -R 644 on files, chmod 755 on directories, and disable PHP engine for that directory via .htaccess or Nginx location blocks).

3. Long-Term Hardening:

   • Implement network segmentation: place any server that accepts file uploads into a DMZ with strict egress control to prevent data exfiltration and lateral movement.
   • Deploy a runtime application self-protection (RASP) agent to detect and block file write attempts to web directories.
   • Enable comprehensive audit logging of file operations and web access; retain logs for at least 90 days.
   • Perform periodic red-team exercises that specifically test upload functionality.
   • Subscribe to CISA KEV and FIRST EPSS feeds to receive real-time alerting if this CVE is added to known-exploited catalogs.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2025-53119 (NVD will publish vendor/version info when disclosed)
2. CWE-434 (Unrestricted Upload of File with Dangerous Type): https://cwe.mitre.org/data/definitions/434.html
3. OWASP File Upload Prevention Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/File_Upload_Cheat_Sheet.html
4. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (no entry for this CVE as of report date)
5. Referer (historical precedent): CVE-2021-41773 (Apache path traversal/file upload chain) analyzed at https://www.cisa.gov/news-events/cybersecurity-advisories/aa21-356a

No known threat actor campaigns or confirmed exploit-in-the-wild evidence are attached to CVE-2025-53119 at the time of this writing; however, the vulnerability class is aggressively targeted by botnets and ransomware affiliates once public disclosure occurs.