# CVE-2026-45372

## Summary

- **CVE ID:** CVE-2026-45372
- **Severity:** CRITICAL
- **CVSS Score:** 9.9 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L)
- **CWE:** CWE-93, CWE-444
- **Published:** May 29, 2026
- **Last Modified:** Jun 1, 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.

## Affected Products

- yhirose — cpp-httplib (< 0.44.0)

## References

- [CNA](https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-xjxg-64p4-vj4m)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.29%
- **EPSS Percentile:** 21.9

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._