CVE-2026-34520

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser (the default for most installs) accepted null bytes and control characters in response headers. This issue has been patched in version 3.13.4.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4	Patch
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4	Release Notes
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf	Patch Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*

History

26 Oct 2026, 21:10

Type	Values Removed	Values Added
Summary		(es) AIOHTTP es un framework HTTP cliente/servidor asíncrono para asyncio y Python. Antes de la versión 3.13.4, el analizador C (el predeterminado para la mayoría de las instalaciones) aceptaba bytes nulos y caracteres de control en las cabeceras de respuesta. Este problema ha sido parcheado en la versión 3.13.4.

Information

Published : 2026-04-01 21:17

Updated : 2026-10-26 21:10

NVD link : CVE-2026-34520

Mitre link : CVE-2026-34520

CVE.ORG link : CVE-2026-34520

JSON object : View

Products Affected

aiohttp

aiohttp

CWE

CWE-113

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

{"id": "CVE-2026-34520", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-34520", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-04-04T03:13:19.553235Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.1, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 5.2, "exploitabilityScore": 3.9}], "cvssMetricV40": [{"type": "Secondary", "source": "security-advisories@github.com", "cvssData": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 2.7, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "LOW", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/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", "exploitMaturity": "UNREPORTED", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "LOW", "integrityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "availabilityRequirement": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "confidentialityRequirement": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED"}}]}, "affected": [{"source": "security-advisories@github.com", "affectedData": [{"vendor": "aio-libs", "product": "aiohttp", "versions": [{"status": "affected", "version": "< 3.13.4"}]}]}], "published": "2026-04-01T21:17:00.333", "references": [{"url": "https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4", "tags": ["Patch"], "source": "security-advisories@github.com"}, {"url": "https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4", "tags": ["Release Notes"], "source": "security-advisories@github.com"}, {"url": "https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf", "tags": ["Patch", "Vendor Advisory"], "source": "security-advisories@github.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "security-advisories@github.com", "description": [{"lang": "en", "value": "CWE-113"}]}], "descriptions": [{"lang": "en", "value": "AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser (the default for most installs) accepted null bytes and control characters in response headers. This issue has been patched in version 3.13.4."}, {"lang": "es", "value": "AIOHTTP es un framework HTTP cliente/servidor as\u00edncrono para asyncio y Python. Antes de la versi\u00f3n 3.13.4, el analizador C (el predeterminado para la mayor\u00eda de las instalaciones) aceptaba bytes nulos y caracteres de control en las cabeceras de respuesta. Este problema ha sido parcheado en la versi\u00f3n 3.13.4."}], "lastModified": "2026-10-26T21:10:00.170", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "7B8B1C30-52F7-467A-A7D0-F6A786E84AF9", "versionEndExcluding": "3.13.4"}], "operator": "OR"}]}], "sourceIdentifier": "security-advisories@github.com"}