---
cve: "CVE-2026-63571"
severity: "HIGH"
cvss: 8.7
epss: "0.2%"
vendor: "Legion of the Bouncy Castle Inc."
kev: false
exploited: false
published: "2026-10-02 08:17:01"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-10-07T05:28:59+02:00"
---

# CVE-2026-63571

> 8.7 HIGH · 🧪 PoC

## Beschreibung

Improper verification of cryptographic signature in the attribute certificate path validator (PkixAttrCertPathValidator, also used by PkixAttrCertPathBuilder) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker to have a forged X.509 attribute certificate accepted as valid, and so obtain whatever roles or privileges an application grants on the strength of its attributes, via an attribute certificate that names a trusted attribute authority as its issuer but was not signed by it, because the RFC 3281 validation steps check the holder and issuer certification paths, validity period, extensions and revocation status but never verify the attribute certificate's signature with the issuer's public key. Only applications that use these classes to validate attribute certificates are affected.

## CNA-Record (Kanon, cvelistV5)

- CNA: **bcorg**
- State: PUBLISHED
- Stand: 2026-10-02 19:16:19
- CNA-CVSS: **8.7** (`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`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **yes**
  - Technical Impact: **partial**

## 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)

- 4007498b13582d90ee1eda5d9920c324428b98b3 (Commit)
- c08f65e1ed7b92a10776220ed9c047f47c264725 (Commit)

## BSI-Hinweise (deutsch)

- [Bouncy Castle: Mehrere Schwachstellen](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-3713) — _BSI-Einstufung: mittel_
  Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Bouncy Castle ausnutzen, um Sicherheitsvorkehrungen zu umgehen, Daten zu manipulieren oder offenzulegen und einen Denial-of-Service-Zustand auszulösen.

## Referenzen

- <https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63571>
- <https://github.com/bcgit/bc-csharp/commit/c08f65e1ed7b92a10776220ed9c047f47c264725>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-63571/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_