---
cve: "CVE-2026-49852"
severity: "HIGH"
cvss: 8.7
epss: "14%"
vendor: "authlib"
kev: false
exploited: false
published: "2026-07-17 19:14:58"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-18T08:39:53+02:00"
---

# CVE-2026-49852

> 8.7 HIGH · 🧪 PoC

## Beschreibung

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8.

## 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
```

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

## Patch verfügbar (OSV)

- 86d00910b2b2d2d07503fee9b572906daefab7f1 (Commit)
- ea1d9e301cc3f6d20d141058e4a0c4befc599b62 (Commit)

## Referenzen

- <https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrh>
- <https://github.com/authlib/joserfc/commit/86d00910b2b2d2d07503fee9b572906daefab7f1>
- <https://github.com/authlib/joserfc/releases/tag/1.6.8>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-49852) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_