---
cve: "CVE-2026-42772"
severity: "MEDIUM"
cvss: 5.3
epss: "0.2%"
vendor: "OpenSSL"
kev: false
exploited: false
published: "2026-09-29 16:17:07"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-10-03T23:31:05+02:00"
---

# CVE-2026-42772

> 5.3 MEDIUM · 🧪 PoC

## Beschreibung

Issue summary: The QUIC stream reassembly algorithm performance deteriorates
progressively as packets are arriving out of order. The worst case has
a quadratic complexity proportional to the number of stream frames kept in
the buffer for the received stream data.

Impact summary: A remote QUIC peer that completes the handshake can create
a connection-scoped CPU pressure and potentially a Denial of Service using
compliant STREAM frames inside the advertised receive window, with low
attacker bandwidth.

CWE: CWE-407: Inefficient Algorithmic Complexity

Description: OpenSSL manages received QUIC stream fragments using a
doubly-linked list. While it optimizes for append operations (at the end of
the list), it falls back to a head-to-tail linear search for any fragment
that does not immediately follow the current `tail`.

By manipulating the sequence of offsets, an attacker can force the server
to perform O(n^2) operations, consuming excessive CPU time for the
QUIC process.

FIPS impact: no
The FIPS module is not affected as the QUIC implementation is outside of
the OpenSSL FIPS module boundary.

## CNA-Record (Kanon, cvelistV5)

- CNA: **openssl**
- State: PUBLISHED
- Stand: 2026-09-30 20:11:09

## CISA-Anreicherung (vulnrichment/ADP)

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

## CVSS-Vektor

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

| 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 | Gering | warn |

## Schwachstellen-Klasse

- **CWE-407** — Inefficient Algorithmic Complexity
  An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

## Patch verfügbar (OSV)

- af1775b60dfa141a4ad762585052cabeb9f37e9e (Commit)
- c8bd5a57108599ac650bbae77fcabe3109dab2e8 (Commit)

## BSI-Hinweise (deutsch)

- [OpenSSL: Mehrere Schwachstellen](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-3638) — _BSI-Einstufung: hoch_
  Ein Angreifer kann mehrere Schwachstellen in OpenSSL ausnutzen, um Sicherheitsvorkehrungen zu umgehen, vertrauliche Informationen offenzulegen, Daten zu manipulieren und einen Denial-of-Service-Zustand zu verursachen.

## Referenzen

- <https://openssl-library.org/news/secadv/20260929.txt>
- <https://github.com/openssl/openssl/commit/f42ae513bbda513b3c121d54834040ee4a0eae1a>
- <https://github.com/openssl/openssl/commit/32d0ed8afe1b8c3e7ece725b44663da3d7087a09>
- <https://github.com/openssl/openssl/commit/ca8402e273af4de5b3f04fa61a0f0c02ce3ae20e>
- <https://github.com/openssl/openssl/commit/eb2becc0a4baea7f3050a247834d0e5c2ebe1773>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-42772) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_