CVE-2026-32239: Capnproto

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 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.

Affected products

• Capnproto Capnproto: before 1.4.0 (fixed in 1.4.0)

Published 2026-03-12. Last modified 2026-06-17.