{"id":"CVE-2026-34520","state":"PUBLISHED","title":"AIOHTTP: C parser (llhttp) accepts null bytes and control characters in response header values - header injection / security bypass","description":"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.","publishedAt":"2026-04-01T20:27:48.350Z","updatedAt":"2026-04-04T03:13:48.418Z","severity":{"score":2.7,"label":"Low","version":"4.0","vector":"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","source":"GitHub_M"},"assigner":"GitHub_M","products":["aio-libs aiohttp"],"affected":[{"vendor":"aio-libs","product":"aiohttp","versions":[{"version":"< 3.13.4","status":"affected"}]}],"references":["https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf","https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4","https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4"],"weaknesses":["CWE-113"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/34xxx/CVE-2026-34520.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-34520","state":"PUBLISHED","datePublished":"2026-04-01T20:27:48.350Z","dateUpdated":"2026-04-04T03:13:48.418Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-30T16:03:31.047Z"},"containers":{"cna":{"title":"AIOHTTP: C parser (llhttp) accepts null bytes and control characters in response header values - header injection / security bypass","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."}],"affected":[{"vendor":"aio-libs","product":"aiohttp","versions":[{"version":"< 3.13.4","status":"affected"}]}],"references":[{"url":"https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf","name":"https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4","name":"https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4","tags":["x_refsource_MISC"]},{"url":"https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4","name":"https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":2.7,"baseSeverity":"LOW","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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-113","lang":"en","description":"CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-04-01T20:27:48.350Z"},"source":{"advisory":"GHSA-63hf-3vf5-4wqf","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"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"}},{"other":{"type":"ssvc","content":{"timestamp":"2026-04-04T03:13:19.553235Z","id":"CVE-2026-34520","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-04T03:13:48.418Z"}}]}}}