---
cve: "CVE-2026-21428"
severity: "HIGH"
cvss: 7.7
epss: "39%"
vendor: "yhirose"
kev: false
exploited: false
published: "2026-01-01 18:15:41"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-05T23:43:06+02:00"
---

# CVE-2026-21428

> 7.7 HIGH · 🧪 PoC

## Beschreibung

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.30.0, the ``write_headers`` function does not check for CR & LF characters in user supplied headers, allowing untrusted header value to escape header lines.
This vulnerability allows attackers to add extra headers, modify request body unexpectedly & trigger an SSRF attack. When combined with a server that supports http1.1 pipelining (springboot, python twisted etc), this can be used for server side request forgery (SSRF). Version 0.30.0 fixes this issue.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- 781c55f120f945d254832660ef9487776b8a90fc (Commit)
- 98048a033a532ff22320ce1d11789f8d5710dfcd (Commit)

## Referenzen

- <https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-wpc6-j37r-jcx7>
- <https://github.com/yhirose/cpp-httplib/commit/98048a033a532ff22320ce1d11789f8d5710dfcd>
- <https://github.com/yhirose/cpp-httplib/releases/tag/v0.30.0>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-21428) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_