{"id":"CVE-2026-34517","aliases":["GHSA-3wq7-rqq7-wx6j","PYSEC-2026-2099"],"title":"AIOHTTP has late size enforcement for non-file multipart fields causes memory DoS","summary":"AIOHTTP has late size enforcement for non-file multipart fields causes memory DoS","severity":"low","vendor":"aiohttp","product":"aiohttp","ecosystem":"pip","affected":["aiohttp < 3.13.4"],"patched":["aiohttp 3.13.4"],"published":"2026-04-01","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:42.683852324Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-3wq7-rqq7-wx6j","references":[{"url":"https://github.com/aio-libs/aiohttp/security/advisories/GHSA-3wq7-rqq7-wx6j"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34517"},{"url":"https://github.com/aio-libs/aiohttp/commit/cbb774f38330563422ca0c413a71021d7b944145"},{"url":"https://github.com/aio-libs/aiohttp"},{"url":"https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4"}],"tags":["osv","pip"],"epss":0.00507,"epssPercentile":0.4062,"ingestedAt":"2026-07-13T18:57:52.125Z","slug":"CVE-2026-34517","body":"## Overview\n\n### Summary\n\nFor some multipart form fields, aiohttp read the entire field into memory before checking client_max_size.\n\n### Impact\n\nIf an application uses `Request.post()` an attacker can send a specially crafted multipart request to force significant temporary memory allocation even when the request is ultimately rejected.\n\n-----\n\nPatch: https://github.com/aio-libs/aiohttp/commit/cbb774f38330563422ca0c413a71021d7b944145\n\n## Affected packages\n\n- `aiohttp < 3.13.4`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `aiohttp 3.13.4`","depth":"sunlit","depthScore":14,"depthScoreParts":{"impact":13.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}