CVE-2026-32239 Details
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.
A vulnerability exists in the KJ-HTTP library, which is part of the Cap'n Proto data interchange format and RPC system, prior to version 1.4.0. The issue arises from a negative 'Content-Length' value being incorrectly converted to an unsigned integer, resulting in an excessively large length. This flaw could potentially facilitate HTTP request/response smuggling. Additionally, when 'Transfer-Encoding: chunked' is used, chunk sizes of 2^64 or larger are truncated to fit within a 64-bit integer, creating another layer of complexity that could be exploited under specific conditions.
Users should update to Cap'n Proto version 1.4.0 or later, where this vulnerability has been fixed. The updated version can be downloaded from the Cap'n Proto website.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Mar 13, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-190 | Integer Overflow or Wraparound | [email protected] |
| CWE-444 | Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| capnproto capnproto | < 1.4.0 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Mar 18, 2026 | Initial Analysis | [email protected] |
| Mar 12, 2026 | New CVE Received | [email protected] |