PT-2026-56210 · Packagist · Egroupware/Egroupware

Publicado

2026-07-07

·

Atualizado

2026-07-07

·

CVE-2026-27823

CVSS v4.0

9.3

Crítica

VetorAV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Summary

A critical vulnerability has been identified in EGroupware that may lead to Remote Code Execution (RCE). The issue allows an authenticated attacker to execute arbitrary commands on the server. If user self-registration is enabled, the vulnerability may be exploitable without prior authentication.
The vulnerability stems from improper authorization checks combined with a file write primitive and an arbitrary file read vulnerability, which together enable full system compromise.

Details

1. Improper Authorization in SmallPartMediaRecorder::ajax upload()

The vulnerability originates in:
EGroupwareSmallParTWidgetsSmallPartMediaRecorder::ajax upload()
The function attempts to verify whether the current user is a teacher of the specified course ID before allowing a file upload.
The critical authorization check ensures that the course access control list (ACL) contains:
$required acl (self::ROLE TEACHER, i.e., 3)
However, the course acl value is derived from user-controlled request data.
** Bypass Technique **
A crafted request can manipulate the participant role value inside the request body:
json
{
 "video": {
  "course id": {
   "participants": [
    {
     "account id": "7",
     "name": "Test",
     "joined at": "2026-01-10",
     "participant role": 3
    }
   ],
   "account id": "7",
   "course id": "1"
  },
  "video hash": ".",
  "video type": "file here"
 }
}
Because the course ACL is taken from participant role, setting it to 3 allows bypassing the isTeacher check.

2. Arbitrary File Write

After bypassing authorization, the function uploads the provided file into a controllable file path.
The file path is derived from the video type (or video path) value, enabling path traversal.
Due to file permission restrictions (server running as www-data), writable targets are limited. One viable target is ./header.inc.php

3. Constraints

Writing a simple PHP webshell may not immediately execute due to OPcache.
An invalid header.inc.php file will break the system and prevent the server from running.
Therefore, a valid file structure must be preserved.

4. Arbitrary File Read

A second vulnerability allows arbitrary file read via:
/egroupware/index.php?menuaction=importexport.importexport export ui.download& filename=../../../usr/share/egroupware/header.inc.php& suffix=txt& type=text/plain&filename=leak
The issue resides in:
importexport export ui::download
The filenameparameter is user-controlled and used to read arbitrary files.
This allows retrieving the original header.inc.php content.

5. Achieving Remote Code Execution

By combining: Arbitrary file read (to retrieve valid header.inc.php); Arbitrary file write (to overwrite it with modified content), an attacker can inject controlled PHP code while preserving file validity.
This results in Remote Code Execution after server restart, or OPcache expiration. An alternative impact includes modifying the admin setup password to gain full system control.

Impact

Remote Code Execution Full system compromise Arbitrary file read Arbitrary file write Potential complete takeover of EGroupware instance

Reported by

This finding was discovered by Huong Kieu of Cenobe Security (https://cenobe.com/)

Correção

IDOR

Path traversal

Code Injection

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Enumeração de Fraquezas

CWE-639CWE-22CWE-94

Identificadores relacionados

CVE-2026-27823
GHSA-H9QX-V5XP-PH8P

Produtos afetados

Egroupware/Egroupware