Medium severity · published Mar 12, 2026
CVE-2026-32239
Cap'n Proto has an integer overflow in KJ-HTTP
6.5
CVSS
0.2%
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 13% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CA
capnproto · capnproto
< 1.4.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-32239
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-32239
Product
https://capnproto.org/capnproto-c++-1.4.0.tar.gz
Product
https://capnproto.org/capnproto-c++-win32-1.4.0.zip
Patch
https://github.com/capnproto/capnproto/commit/2744b3c012b4aa3c31cefb61ec656829fa5c0e36
Patch
https://github.com/capnproto/capnproto/commit/e929f0ba7901a6b8f4b5ba9a4db00af43288cbb0
Vendor Advisory
https://github.com/capnproto/capnproto/security/advisories/GHSA-qjx3-pp3m-9jpm
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