Unrated severityNVD Advisory· Published Mar 12, 2026· Updated Mar 13, 2026
Cap'n Proto: Integer overflow in KJ-HTTP chunk size
CVE-2026-32240
Description
Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, when using Transfer-Encoding: chunked, if a chunk's size parsed to a value of 2^64 or larger, it would be truncated to a 64-bit integer. In theory, this bug could enable HTTP request/response smuggling. This vulnerability is fixed in 1.4.0.
Affected products
2Patches
Vulnerability mechanics
References
5- capnproto.org/capnproto-c++-1.4.0.tar.gzmitrex_refsource_MISC
- capnproto.org/capnproto-c++-win32-1.4.0.zipmitrex_refsource_MISC
- github.com/capnproto/capnproto/commit/2744b3c012b4aa3c31cefb61ec656829fa5c0e36mitrex_refsource_MISC
- github.com/capnproto/capnproto/commit/e929f0ba7901a6b8f4b5ba9a4db00af43288cbb0mitrex_refsource_MISC
- github.com/capnproto/capnproto/security/advisories/GHSA-vpcq-mx5v-32wmmitrex_refsource_CONFIRM
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