CVE-2026-34516High· 7.5▾ TwilightAIOHTTP has a Multipart Header Size Bypass
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 41.3 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 13.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
0.4%
Last analysed / modified upstream
A response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability.
Multipart headers were not subject to the same size restrictions in place for normal headers, potentially allowing substantially more data to be loaded into memory than intended. However, other restrictions in place limit the impact of this vulnerability.
Patch: https://github.com/aio-libs/aiohttp/commit/8a74257b3804c9aac0bf644af93070f68f6c5a6f
aiohttp < 3.13.4Upgrade to a patched release:
aiohttp 3.13.4Connected by shared product, vendor, weakness, or advisory.
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