# CVE-2026-45372: libcpp-httplib0: cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library

CVE-2026-45372 is fixed in 6 products on 1 platform, first by libcpp-httplib0.26 0.26.0+ds-2ubuntu3+esm1, released May 29, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-45372
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0030
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 29, 2026

## Description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The validity check (is_field_value) is run before decoding, so encoded %0D%0A passes the check and is then expanded to a literal \r\n byte pair inside the stored header value. This vulnerability is fixed in 0.44.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | cpp-httplib Fedora 43 | 0.48.0-1.fc43 | [FEDORA-2026-1D4BD0354A](https://patchblox.com/security/data/fix/linux/fedora-2026-1d4bd0354a.md) | Jun 24, 2026 |
| Linux | cpp-httplib-devel Fedora 43 | 0.48.0-1.fc43 | [FEDORA-2026-1D4BD0354A](https://patchblox.com/security/data/fix/linux/fedora-2026-1d4bd0354a.md) | Jun 24, 2026 |
| Linux | libcpp-httplib0 Ubuntu 22.04.1 LTS (jammy) | 0.10.3+ds-1ubuntu0.1~esm2 | [libcpp-httplib0 0.10.3+ds-1ubuntu0.1~esm2](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libcpp-httplib0-0.10.3-ds-1ubuntu0.1-esm2.md) | Jun 26, 2026 |
| Linux | libcpp-httplib0.14t64 Ubuntu 24.04.5 LTS (noble) | 0.14.3+ds-1.1ubuntu0.1~esm2 | [libcpp-httplib0.14t64 0.14.3+ds-1.1ubuntu0.1~esm2](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libcpp-httplib0.14t64-0.14.3-ds-1.1ubuntu0.1-esm2.md) | Jun 26, 2026 |
| Linux | libcpp-httplib0.18 Ubuntu 25.10 (questing) | 0.18.7-1ubuntu0.25.10.2 | [libcpp-httplib0.18 0.18.7-1ubuntu0.25.10.2](https://patchblox.com/security/data/fix/linux/ubuntu-questing-libcpp-httplib0.18-0.18.7-1ubuntu0.25.10.2.md) | Jun 26, 2026 |
| Linux | libcpp-httplib0.26 Ubuntu 26.04.1 LTS (resolute) | 0.26.0+ds-2ubuntu3+esm1 | [libcpp-httplib0.26 0.26.0+ds-2ubuntu3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libcpp-httplib0.26-0.26.0-ds-2ubuntu3-esm1.md) | May 29, 2026 |

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Data as of 2026-11-08T00:53:09Z 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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