---
cve: "CVE-2026-42786"
severity: "HIGH"
cvss: 8.7
epss: "55%"
vendor: "mtrudel"
kev: false
exploited: false
published: "2026-05-01 21:16:17"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-10T09:08:56+02:00"
---

# CVE-2026-42786

> 8.7 HIGH · 🧪 PoC

## Beschreibung

Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion.

The fragment reassembly path in 'Elixir.Bandit.WebSocket.Connection':handle_frame/3 in lib/bandit/websocket/connection.ex appends every incoming Continuation{fin: false} frame's payload to a per-connection iolist with no cumulative size cap. The existing max_frame_size option only bounds individual frames; a peer that streams an unbounded number of continuation frames without ever setting fin=1 grows BEAM heap linearly until the OS or a supervisor kills the process.

Because the accumulation happens before WebSock.handle_in/2 is called, the application has no opportunity to interpose a size check. Phoenix Channels and LiveView both run over WebSock on Bandit, so a stock Phoenix application exposes this surface as soon as it accepts socket connections.

This issue affects bandit: from 0.5.0 before 1.11.0.

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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)

- e62619895d0d2584d7ffa57d43ef6f72437dfaff (Commit)
- 21612c7c7b1ce43eccd36d3af3a2299d23513667 (Commit)

## Referenzen

- <https://github.com/mtrudel/bandit/security/advisories/GHSA-pf94-94m9-536p>
- <https://cna.erlef.org/cves/CVE-2026-42786.html>
- <https://osv.dev/vulnerability/EEF-CVE-2026-42786>
- <https://github.com/mtrudel/bandit/commit/21612c7c7b1ce43eccd36d3af3a2299d23513667>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-42786) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_