---
cve: "CVE-2026-34950"
severity: "CRITICAL"
cvss: 9.1
epss: "0.3%"
vendor: "nearform"
kev: false
exploited: false
published: "2026-04-06 16:16:38"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-10-25T01:05:24+02:00"
---

# CVE-2026-34950

> 9.1 CRITICAL · 🧪 PoC

## Beschreibung

fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher regex in fast-jwt/src/crypto.js uses a ^ anchor that is defeated by any leading whitespace in the key string, re-enabling the exact same JWT algorithm confusion attack that CVE-2023-48223 patched.

## CNA-Record (Kanon, cvelistV5)

- CNA: **GitHub_M**
- State: PUBLISHED
- Stand: 2026-04-06 18:43:16
- CNA-CVSS: **9.1** (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **poc**
  - Automatable: **yes**
  - Technical Impact: **total**

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Keine | good |

## Schwachstellen-Klasse

- **CWE-327** — Use of a Broken or Risky Cryptographic Algorithm
  The product uses a broken or risky cryptographic algorithm or protocol.

## Angriffsmuster (CAPEC)

- [CAPEC-20 — Encryption Brute Forcing](https://capec.mitre.org/data/definitions/20.html) _(Severity: Low)_
- [CAPEC-97 — Cryptanalysis](https://capec.mitre.org/data/definitions/97.html) _(Severity: Very High)_
- [CAPEC-459 — Creating a Rogue Certification Authority Certificate](https://capec.mitre.org/data/definitions/459.html) _(Severity: Very High)_
- [CAPEC-473 — Signature Spoof](https://capec.mitre.org/data/definitions/473.html)
- [CAPEC-475 — Signature Spoofing by Improper Validation](https://capec.mitre.org/data/definitions/475.html) _(Severity: High)_
- [CAPEC-608 — Cryptanalysis of Cellular Encryption](https://capec.mitre.org/data/definitions/608.html) _(Severity: High)_
- [CAPEC-614 — Rooting SIM Cards](https://capec.mitre.org/data/definitions/614.html) _(Severity: High)_

## ATT&CK-Techniken

- [T1036.001 — Masquerading: Invalid Code Signature](https://attack.mitre.org/techniques/T1036/001/)
- [T1553.002 — Subvert Trust Controls: Code Signing](https://attack.mitre.org/techniques/T1553/002/)

## Patch verfügbar (OSV)

- e07b1fd23f02a47f1be677a21a4f07607b478e66 (Commit)

## Referenzen

- <https://github.com/nearform/fast-jwt/security/advisories/GHSA-mvf2-f6gm-w987>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-34950/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_