Overview
CVE-2026-48356 is a critical unrestricted file upload vulnerability (CWE-434) impacting Adobe Commerce and Magento. Successful exploitation allows for arbitrary code execution in the context of the current user, potentially leading to elevated access or session control. This vulnerability is actively exploited, with observed post-exploitation activity involving CMS block loaders and malicious JavaScript injection.
Technical Analysis
- Vulnerability: CWE-434: Unrestricted Upload of File with Dangerous Type.
- Affected Products: The vulnerability affects multiple versions of Adobe Commerce and Adobe Commerce B2B:
- Adobe Commerce:
2.4.4,2.4.5,2.4.6,2.4.7,2.4.8,2.4.9 - Adobe Commerce B2B:
1.3.3,1.3.4,1.4.2,1.5.2
- Adobe Commerce:
- Attack Vector: Remote, network-based. Exploitation requires user interaction, where a victim must visit a maliciously crafted URL or interact with a compromised web page. This interaction facilitates the upload of a dangerous file type.
- Impact: Arbitrary code execution in the context of the current user, potentially gaining elevated access or control over the victim’s account or session. This can lead to web shell deployment, data exfiltration, and further system compromise.
- CVSS 3.1 Score:
9.3 (CRITICAL)with vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.
Detection
- Monitor web server logs (e.g., Apache, Nginx, IIS) for HTTP
POSTrequests to unexpected directories containing file extensions typically associated with server-side scripts (e.g.,.php,.phtml,.jsp,.asp). - Look for web server processes (e.g.,
php-fpm.exe,httpd.exe,nginx.exe,w3wp.exe) spawning unusual child processes such ascmd.exe,powershell.exe,sh,bash,python.exe, orperl.exe(Sysmon Event ID 1). - Monitor file system events for new files with dangerous extensions (e.g.,
.php,.phtml) being written to web-accessible directories by the web server process, especially outside of expected upload paths (Sysmon Event ID 11). - Scan web server directories for known web shell signatures or suspicious file content.
- Monitor network traffic for outbound connections initiated by the web server process to unusual external IP addresses or domains.
- Review web access logs for requests to newly created or suspicious script files in web root directories, indicative of web shell access (e.g.,
GET /media/catalog/product/cache/1/image/web_shell.php?cmd=id).
Sigma Detection Rules
⚠️ AI-generated detection rules. These are experimental starting points. Review field names, EventIDs, and logic against your environment’s schema before deploying. Tune to reduce false positives.
Web Server Process Spawning Shell
title: Web Server Process Spawning Shell
id: 5a7b8c9d-e0f1-2345-6789-abcd1234ef01
status: experimental
description: Detects a web server process (e.g., PHP-FPM, Apache, Nginx) spawning a command shell, indicative of arbitrary code execution.
logsource:
product: windows
service: sysmon
detection:
selection_parent:
ParentImage|endswith:
- '\php-fpm.exe'
- '\httpd.exe'
- '\nginx.exe'
- '\w3wp.exe'
selection_child:
Image|endswith:
- '\cmd.exe'
- '\powershell.exe'
- '\pwsh.exe'
- '\sh.exe'
- '\bash.exe'
- '\python.exe'
- '\perl.exe'
condition: all of selection_*
level: critical
Suspicious File Creation by Web Server Process
title: Suspicious File Creation by Web Server Process
id: 1f2e3d4c-5b6a-7890-1234-56789abcdef0
status: experimental
description: Detects a web server process creating suspicious files with dangerous extensions in web-accessible directories, potentially indicating a web shell upload.
logsource:
product: windows
service: sysmon
detection:
selection_image:
Image|endswith:
- '\php-fpm.exe'
- '\httpd.exe'
- '\nginx.exe'
- '\w3wp.exe'
selection_filename:
TargetFilename|endswith:
- '.php'
- '.phtml'
- '.jsp'
- '.asp'
- '.aspx'
selection_path:
TargetFilename|contains:
- '\inetpub\wwwroot\'
- '\var\www\html\'
- '\magento\pub\media\'
- '\magento\var\'
- '\upload\'
- '\cache\'
condition: all of selection_*
level: high
Web Access to Suspicious Script Files in Web Roots
title: Web Access to Suspicious Script Files in Web Roots
id: 9a8b7c6d-5e4f-3210-fedc-ba9876543210
status: experimental
description: Detects HTTP requests to suspicious script files in web-accessible directories, potentially indicating web shell access or post-exploitation activity.
logsource:
category: webserver
detection:
selection_uri:
cs-uri-stem|contains:
- '/shell.php'
- '/cmd.php'
- '/upload.php'
- '/backdoor.php'
- '/eval.php'
- '/wso.php'
- '/c99.php'
- '/r57.php'
- '/magento/pub/media/'
- '/magento/var/'
selection_method:
cs-method: 'POST'
condition: selection_uri or (selection_uri and selection_method)
level: high
Mitigations
- Patch Immediately: Apply the latest security patches from Adobe for all affected Adobe Commerce and Magento installations. Refer to the vendor advisory
https://helpx.adobe.com/security/products/magento/apsb26-73.html. - Restrict File Uploads: Implement strict validation and sanitization for all user-uploaded files, including type, size, and content. Restrict executable file types from being uploaded to web-accessible directories.
- Principle of Least Privilege: Ensure the web server process runs with the minimum necessary privileges.
- Web Application Firewall (WAF): Deploy and configure a WAF to detect and block suspicious file uploads and requests to known web shell patterns.
- File Integrity Monitoring (FIM): Implement FIM on web server directories to alert on unauthorized creation or modification of files.
- Regular Audits: Periodically audit web server directories for unauthorized files.
References
- https://helpx.adobe.com/security/products/magento/apsb26-73.html
- https://nvd.nist.gov/vuln/detail/CVE-2026-48356
- https://sansec.io/research/magento-cms-block-loader-deepveindrilling#indicators-of-compromise
- https://sansec.io/research/polyshell-mass-attack-wave
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48356
- https://ltna.com.au/cyber
Indicators of Compromise
| Type | Value | Description |
|---|---|---|
| Domain | deepveindrilling.com |
Domain associated with post-exploitation CMS block loader activity. |
MITRE ATT&CK
T1190— Exploit Public-Facing ApplicationT1505.003— Web ShellT1059— Command and Scripting InterpreterT1059.007— JavaScriptT1539— Steal Web Session CookieT1074.001— Local Data StagingT1566.002— Spearphishing LinkT1005— Data from Local SystemT1140— Deobfuscate/Decode Files or InformationT1218— System Binary Proxy ExecutionT1136.001— Local AccountT1056.003— Web Portal CaptureT1087.004— Cloud AccountT1098— Account ManipulationT1027— Obfuscated Files or InformationT1573— Encrypted ChannelT1567.002— Exfiltration to Cloud StorageT1070.004— File DeletionT1071.001— Web ProtocolsT1204.001— Malicious LinkT1078.003— Local Accounts
🤖 AI Attribution
Generated by
2,122 input / 2,212 output tokens ·
Reviewed and approved by a human analyst before publication
Generated by
gemini-2.5-flash ·2,122 input / 2,212 output tokens ·
Reviewed and approved by a human analyst before publication