Medium 6.3Published Mar 12, 2026

CVE-2026-32239Cap'n Proto has an integer overflow in KJ-HTTP

Updated under an hour ago (Oct 26, 2026, 11:25 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for capnproto

Exploited in the last 30 days

Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, a negative Content-Length value was converted to unsigned, treating it as an impossibly large length instead. In theory, this bug could enable HTTP request/response smuggling. This vulnerability is fixed in 1.4.0.

CVSS: 6.3 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Weakness (CWE): CWE-444, CWE-190
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Mar 13, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

capnproto capnproto capnproto:capnproto (from the name)	before 1.4.0	CNA record
capnproto capnproto capnproto:capnproto	before 1.4.0	NVD

References

References

https://github.com/capnproto/capnproto/security/advisories/GHSA-qjx3-pp3m-9jpm	x-refsource-confirm, vendor-advisory
https://github.com/capnproto/capnproto/commit/2744b3c012b4aa3c31cefb61ec656829fa5c0e36	x-refsource-misc, patch
https://github.com/capnproto/capnproto/commit/e929f0ba7901a6b8f4b5ba9a4db00af43288cbb0	x-refsource-misc, patch
https://capnproto.org/capnproto-c++-1.4.0.tar.gz	x-refsource-misc, product
https://capnproto.org/capnproto-c++-win32-1.4.0.zip	x-refsource-misc, product

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.