mtrudel bandit up to 1.10.x connection.ex Elixir.Bandit.WebSocket.Connection allocation of resources

Summaryinfo

A vulnerability identified as problematic has been detected in mtrudel bandit up to 1.10.x. Affected by this vulnerability is the function Elixir.Bandit.WebSocket.Connection in the library lib/bandit/websocket/connection.ex. Performing a manipulation results in allocation of resources. This vulnerability is cataloged as CVE-2026-42786. It is possible to initiate the attack remotely. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in mtrudel bandit up to 1.10.x. It has been classified as problematic. This affects the function Elixir.Bandit.WebSocket.Connection in the library lib/bandit/websocket/connection.ex. The manipulation with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. This is going to have an impact on availability. The summary by CVE is:

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.

The weakness was shared by Peter Ullrich and Jonatan Männchen as GHSA-pf94-94m9-536p. The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-42786 since 04/29/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 1.11.0 eliminates this vulnerability. Applying the patch 21612c7c7b1ce43eccd36d3af3a2299d23513667 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-26715). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• mtrudel

Name

• bandit

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10

License

• open-source

Website

• Product: https://github.com/mtrudel/bandit/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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