{"action":"Upgrade aiohttp to 3.13.4 or later.","affected":[{"fixed":"3.13.4","introduced":"0"}],"component":"aiohttp","cve_ids":["CVE-2026-34520"],"ecosystem":"PyPI","epss":0.00479,"exploited":false,"fixed_versions":["3.13.4"],"ghsa_id":"GHSA-63hf-3vf5-4wqf","id":"tcs_01M5KF28XKBTZKN4G2Q6H8EE9T","modified_at":"2026-09-10T03:50:43.255807027Z","published_at":"2026-04-01T21:49:06Z","references":["https://osv.dev/vulnerability/GHSA-63hf-3vf5-4wqf","https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf","https://nvd.nist.gov/vuln/detail/CVE-2026-34520","https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4","https://github.com/aio-libs/aiohttp","https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4","https://github.com/pypa/advisory-database/tree/main/vulns/aiohttp/PYSEC-2026-2102.yaml"],"severity":{"label":"critical","score":9.1},"sources":[{"source":"osv","source_id":"GHSA-63hf-3vf5-4wqf","url":"https://osv.dev/vulnerability/GHSA-63hf-3vf5-4wqf"}],"summary":"AIOHTTP's C parser (llhttp) accepts null bytes and control characters in response header values - header injection/security bypass"}