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EGroupware has a Remote Code Execution Vulnerability

Critical severity GitHub Reviewed Published Jul 6, 2026 in EGroupware/egroupware • Updated Jul 7, 2026

Package

composer egroupware/egroupware (Composer)

Affected versions

>= 26.0.20251208, < 26.2.20260224
< 23.1.20260224

Patched versions

26.2.20260224
23.1.20260224

Description

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:

EGroupware\SmallParT\Widgets\SmallPartMediaRecorder::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:

{
  "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 _filename parameter 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/)

References

@ralfbecker ralfbecker published to EGroupware/egroupware Jul 6, 2026
Published to the GitHub Advisory Database Jul 7, 2026
Reviewed Jul 7, 2026
Last updated Jul 7, 2026

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(61st percentile)

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Learn more on MITRE.

Improper Control of Generation of Code ('Code Injection')

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. Learn more on MITRE.

Authorization Bypass Through User-Controlled Key

The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. Learn more on MITRE.

CVE ID

CVE-2026-27823

GHSA ID

GHSA-h9qx-v5xp-ph8p

Source code

Credits

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