CVE-2026-114213: WebSocket 1-byte continuation frames bypass `max_fragmented_message_size` in Bandit

Published Oct 26, 2026
·
Updated

Allocation of Resources Without Limits or Throttling vulnerability in the WebSocket fragment reassembly of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a fragmented message made of many 1-byte continuation frames.

Bandit.WebSocket.Connection checks maxfragmentedmessagesize against the payload bytes received, but keeps every non-final continuation frame as a new list cell around its own binary, and nothing limits the number of fragments. A 1-byte fragment costs 7 bytes on the wire but about 150 to 170 bytes of server memory, so one connection can hold about 150 times the configured limit, roughly 1.2 to 1.4 GB at the default 8 MB. Ping frames between fragments keep the connection alive past the idle timeout.

This issue affects bandit: from 1.11.0 before 1.14.0.

Affected Software

1 affected component
hex/bandit>=1.11.0<1.14.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade bandit to a version that resolves this vulnerability.

    Fixed in 1.14.0

Event History

Oct 26, 2026
CVE Published
via MITRE·01:30 PM
Data Sourced
via MITRE·01:30 PM
DescriptionWeakness

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