CVE-2026-42786
Severity CVSS v4.0:
HIGH
Type:
Unavailable / Other
Publication date:
01/05/2026
Last modified:
05/05/2026
Description
Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion.<br />
<br />
The fragment reassembly path in &#39;Elixir.Bandit.WebSocket.Connection&#39;:handle_frame/3 in lib/bandit/websocket/connection.ex appends every incoming Continuation{fin: false} frame&#39;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.<br />
<br />
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.<br />
<br />
This issue affects bandit: from 0.5.0 before 1.11.0.
Impact
Base Score 4.0
8.70
Severity 4.0
HIGH
References to Advisories, Solutions, and Tools
- https://cna.erlef.org/cves/CVE-2026-42786.html
- https://github.com/mtrudel/bandit/commit/21612c7c7b1ce43eccd36d3af3a2299d23513667
- https://github.com/mtrudel/bandit/security/advisories/GHSA-pf94-94m9-536p
- https://osv.dev/vulnerability/EEF-CVE-2026-42786
- https://github.com/mtrudel/bandit/security/advisories/GHSA-pf94-94m9-536p