---
cve: "CVE-2026-63072"
severity: "HIGH"
cvss: 7.5
epss: "68%"
vendor: "OpenSSL"
kev: false
exploited: false
published: "2026-08-25 13:19:26"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-18T00:34:26+02:00"
---

# CVE-2026-63072

> 7.5 HIGH · 🧪 PoC

## Beschreibung

Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based
on querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive
can write and cleanse more bytes than that query reports, causing an 8-byte
out-of-bounds heap write.

Impact summary: An attacker who supplies a crafted CMS message can trigger a
deterministic 8-byte out-of-bounds heap write when the victim decrypts it
with CMS_decrypt(), corrupting the heap and typically resulting in a Denial
of Service.

CWE: CWE-787: Out-of-bounds Write

Description: The key-wrap OID is potentially attacker-controlled on the wire.
CMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers.
An attacker can take a legitimate message and change a single OID byte to
select the padded variant while leaving the message otherwise valid. Since
the unwrap key is derived from the recipient's private operation (ECDH key
agreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot
pass, and the decryption fails with integrity failure.

The write is a fixed-size (8-byte), fixed-value (zero) heap overflow
immediately past the allocation, requires no special configuration, and is
reachable from the public CMS_decrypt() function. The consequence is
a heap corruption leading to a Denial of Service. The fix in the CMS code
sizes the unwrap output buffer for the worst case so a failed unwrap cannot
write past the allocation.

FIPS impact: no

As the CMS code lives outside the FIPS module boundary, no FIPS
modules are affected by this CVE.

## CVSS-Vektor

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

| 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 | Keine | good |
| I Integrität | Keine | good |
| A Verfügbarkeit | Hoch | bad |

## Schwachstellen-Klasse

- **CWE-787** — Out-of-bounds Write
  The product writes data past the end, or before the beginning, of the intended buffer.

## Patch verfügbar (OSV)

- a279090b9cd6b682a5a178410765a63e619fa2d9 (Commit)
- 0c5d912057abf47505b4ad455da49fbab99b76f1 (Commit)

## Referenzen

- <https://openssl-library.org/news/secadv/20260825.txt>
- <https://github.com/openssl/openssl/commit/9530a5fd1aacaeccdced4478ea2340a480613335>
- <https://github.com/openssl/openssl/commit/2a3dac874c8057c1f0186849bf1ede1ae7b6b756>
- <https://github.com/openssl/openssl/commit/87784ad619af36b8807c2044b3940006fccc1e42>
- <https://github.com/openssl/openssl/commit/9ec2f6d2ae2bcad907cf7ee38584855bafe4979a>
- <https://github.com/openssl/openssl/commit/a0c8ec557d9cac078f032d76cdf684fe743eb382>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-63072) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_