# CVE-2026-32240: capnproto: Cap'n Proto is a data interchange format and capability-based RPC system

CVE-2026-32240 is fixed in 6 products on 1 platform, first by capnproto 0.6.1-1ubuntu1+esm1, released March 12, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-32240
- Priority: Routine
- CVSS: 6.5 (Medium)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 12, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | capnproto Debian 14 | 1.4.0-2 | [DEBIAN-CVE-2026-32240](https://patchblox.com/security/data/fix/linux/debian-cve-2026-32240.md) | Mar 12, 2026 |
| Linux | capnproto Ubuntu 18.04.6 LTS (bionic) | 0.6.1-1ubuntu1+esm1 | [capnproto 0.6.1-1ubuntu1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-capnproto-0.6.1-1ubuntu1-esm1.md) | Mar 12, 2026 |
| Linux | capnproto Ubuntu 20.04 LTS (focal) | 0.7.0-6ubuntu0.1~esm1 | [capnproto 0.7.0-6ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-capnproto-0.7.0-6ubuntu0.1-esm1.md) | Mar 12, 2026 |
| Linux | capnproto Ubuntu 22.04.1 LTS (jammy) | 0.8.0-2ubuntu2+esm1 | [capnproto 0.8.0-2ubuntu2+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-capnproto-0.8.0-2ubuntu2-esm1.md) | Mar 12, 2026 |
| Linux | capnproto Ubuntu 24.04.5 LTS (noble) | 1.0.1-4ubuntu0.1~esm1 | [capnproto 1.0.1-4ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-capnproto-1.0.1-4ubuntu0.1-esm1.md) | Mar 12, 2026 |
| Linux | capnproto Ubuntu 26.04.1 LTS (resolute) | 1.1.0-2.1ubuntu0.1~esm1 | [capnproto 1.1.0-2.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-capnproto-1.1.0-2.1ubuntu0.1-esm1.md) | Mar 12, 2026 |
| Linux | capnproto opensuse-leap 16.0 | 1.4.0-160000.1.1 | [OPENSUSE-SU-2026:21062-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21062-1.md) | Jun 26, 2026 |
| Linux | libcapnp-0.6.1 Ubuntu 18.04.6 LTS (bionic) | 0.6.1-1ubuntu1+esm1 | [libcapnp-0.6.1 0.6.1-1ubuntu1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libcapnp-0.6.1-0.6.1-1ubuntu1-esm1.md) | Mar 12, 2026 |
| Linux | libcapnp-0.7.0 Ubuntu 20.04 LTS (focal) | 0.7.0-6ubuntu0.1~esm1 | [libcapnp-0.7.0 0.7.0-6ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libcapnp-0.7.0-0.7.0-6ubuntu0.1-esm1.md) | Mar 12, 2026 |
| Linux | libcapnp-0.8.0 Ubuntu 22.04.1 LTS (jammy) | 0.8.0-2ubuntu2+esm1 | [libcapnp-0.8.0 0.8.0-2ubuntu2+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libcapnp-0.8.0-0.8.0-2ubuntu2-esm1.md) | Mar 12, 2026 |
| Linux | libcapnp-1.0.1 Ubuntu 24.04.5 LTS (noble) | 1.0.1-4ubuntu0.1~esm1 | [libcapnp-1.0.1 1.0.1-4ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libcapnp-1.0.1-1.0.1-4ubuntu0.1-esm1.md) | Mar 12, 2026 |
| Linux | libcapnp-1.1.0 Ubuntu 26.04.1 LTS (resolute) | 1.1.0-2.1ubuntu0.1~esm1 | [libcapnp-1.1.0 1.1.0-2.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libcapnp-1.1.0-1.1.0-2.1ubuntu0.1-esm1.md) | Mar 12, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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