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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.

PUBLISHED Reserved 2026-03-11 | Published 2026-03-12 | Updated 2026-03-13 | Assigner GitHub_M




MEDIUM: 6.3CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Problem types

CWE-197: Numeric Truncation Error

CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Product status

< 1.4.0
affected

References

github.com/...nproto/security/advisories/GHSA-vpcq-mx5v-32wm

github.com/...ommit/2744b3c012b4aa3c31cefb61ec656829fa5c0e36

github.com/...ommit/e929f0ba7901a6b8f4b5ba9a4db00af43288cbb0

capnproto.org/capnproto-c++-1.4.0.tar.gz

capnproto.org/capnproto-c++-win32-1.4.0.zip

cve.org (CVE-2026-32240)

nvd.nist.gov (CVE-2026-32240)

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