---
cve: "CVE-2026-75870"
severity: "CRITICAL"
cvss: 9.1
epss: "0.5%"
vendor: "Generic Security"
kev: false
exploited: false
published: "2026-08-22 14:16:33"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-24T11:21:39+02:00"
---

# CVE-2026-75870

> 9.1 CRITICAL

## Beschreibung

Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret.

The session keyword freezes its options onto the application as given: it does not require a secret, warn, or refuse to start when one is absent. The cookie read and the write-back both default that key to the empty string, so a declaration with no secret option, or with an undefined or empty one, signs and verifies with a zero-length HMAC-SHA256 key.

An attacker who knows the cookie format can then mint one offline carrying any contents the session holds, such as a user identifier or a role. Nothing marks the misconfiguration at runtime: cookies are well formed and sessions round-trip as expected.

## 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 |

## Referenzen

- <https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h>
- <https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm>
- <https://metacpan.org/release/LNATION/Punk-0.18/source/Changes>
- <http://www.openwall.com/lists/oss-security/2026/08/22/5>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-75870) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_