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.
References (5)
Core 5
Core References
Vendor Advisory x_refsource_confirm
https://github.com/capnproto/capnproto/security/advisories/GHSA-vpcq-mx5v-32wm
Patch x_refsource_misc
https://github.com/capnproto/capnproto/commit/2744b3c012b4aa3c31cefb61ec656829fa5c0e36
Patch x_refsource_misc
https://github.com/capnproto/capnproto/commit/e929f0ba7901a6b8f4b5ba9a4db00af43288cbb0
Various Sources x_refsource_misc
https://capnproto.org/capnproto-c++-1.4.0.tar.gz
Various Sources x_refsource_misc
https://capnproto.org/capnproto-c++-win32-1.4.0.zip
Scores
CVSS v3
6.5
EPSS
0.0021
EPSS Percentile
10.7%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-444
CWE-197
Status
published
Products (1)
capnproto/capnproto
< 1.4.0
Published
Mar 12, 2026
Tracked Since
Mar 13, 2026