---
cve: "CVE-2026-81535"
severity: "MEDIUM"
cvss: 6.3
epss: "0.3%"
vendor: "wolfSSL Inc."
kev: false
exploited: false
published: "2026-10-07 03:16:59"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-10-23T23:14:30+02:00"
---

# CVE-2026-81535

> 6.3 MEDIUM · 🧪 PoC

## Beschreibung

In wolfSSH through 1.5.0 built with --enable-fwd, DoChannelOpen() in src/internal.c gates only direct-tcpip channel opens with the forwarding policy callback. forwarded-tcpip opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a forwarded-tcpip open against the forwards it registered with a tcpip-forward request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.

## CNA-Record (Kanon, cvelistV5)

- CNA: **wolfSSL**
- State: PUBLISHED
- Stand: 2026-10-07 18:37:36
- CNA-CVSS: **6.3** (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **no**
  - Technical Impact: **partial**

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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 |

## Schwachstellen-Klasse

- **CWE-862** — Missing Authorization
  The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
- **CWE-863** — Incorrect Authorization
  The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

## Angriffsmuster (CAPEC)

- [CAPEC-665 — Exploitation of Thunderbolt Protection Flaws](https://capec.mitre.org/data/definitions/665.html) _(Severity: Very High)_

## ATT&CK-Techniken

- [T1211 — Exploitation for Defensive Evasion](https://attack.mitre.org/techniques/T1211/)
- [T1542.002 — Pre-OS Boot: Component Firmware](https://attack.mitre.org/techniques/T1542/002/)
- [T1556 — Modify Authentication Process](https://attack.mitre.org/techniques/T1556/)

## Patch verfügbar (OSV)

- 8221e4ee48c93da6cea3325a91de2ecc00ae5f56 (Commit)
- 616eb681e70759c30c3ba158f2b18d7bd954def8 (Commit)

## Referenzen

- <https://github.com/wolfSSL/wolfssh/commit/616eb681e70759c30c3ba158f2b18d7bd954def8>
- <https://github.com/wolfSSL/wolfssh/commit/e396a0a4b6b367f10270287446a4be0071742b5c>
- <https://github.com/wolfSSL/wolfssh/commit/79a7f299337a28aa561409688a268d0efe6e295c>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-81535/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_