CVE-2026-114213
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Allocation of Resources Without Limits or Throttling in Bandit WebSocket Fragment Reassembly

Publication date: 2026-10-26

Last updated on: 2026-10-26

Assigner: EEF

Description
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 max_fragmented_message_size 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.

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Meta Information

Published
2026-10-26
Last Modified
2026-10-26
Generated
2026-10-26
AI Q&A
2026-10-26
EPSS Evaluated
N/A
NVD
CVE-2026-114213
EUVD
EUVD-2026-109821

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
mtrudel bandit 1.11.0
mtrudel bandit 21612c7c7b1ce43eccd36d3af3a2299d23513667

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Attack-Flow Graph

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Executive Summary

CVE-2026-114213 is a memory exhaustion vulnerability in the Bandit WebSocket library. An unauthenticated attacker can send fragmented WebSocket messages with many 1-byte continuation frames. Each frame consumes about 150-170 bytes of server memory, allowing an attacker to exceed the configured message size limit significantly. For example, with the default 8 MB limit, a single connection could use up to 1.2-1.4 GB of memory. Ping frames keep the connection alive, bypassing idle timeouts.

Detection Guidance

Monitor for unusually high memory usage on servers running Bandit WebSocket connections. Check for fragmented WebSocket messages with many small continuation frames using tools like Wireshark or tcpdump to capture and analyze network traffic for abnormal WebSocket fragmentation patterns.

Impact Analysis

This vulnerability can lead to denial-of-service (DoS) conditions by consuming excessive server memory. It affects any Bandit server accepting WebSocket upgrades, including those using Phoenix LiveView or Channels. Attackers can exhaust server resources, causing crashes or degraded performance for legitimate users.

Mitigation Strategies
  • Upgrade Bandit to version 1.14.0 or later to apply the security patch addressing the fragment reassembly issue.
  • Reduce the max_fragmented_message_size setting in WebSocket options to a lower value to limit memory consumption per connection.
  • Implement network-level monitoring to detect and block suspicious WebSocket fragmentation patterns.

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