CVE-2026-32240

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.

• CWE-197
• CWE-444

• https://capnproto.org/capnproto-c++-1.4.0.tar.gzProduct
• https://capnproto.org/capnproto-c++-win32-1.4.0.zipProduct
• https://github.com/capnproto/capnproto/commit/2744b3c012b4aa3c31cefb61ec656829fa5c0e36Patch
• https://github.com/capnproto/capnproto/commit/e929f0ba7901a6b8f4b5ba9a4db00af43288cbb0Patch
• https://github.com/capnproto/capnproto/security/advisories/GHSA-vpcq-mx5v-32wmVendor Advisory

Published

Mar 12, 2026

Last Modified

Jun 17, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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