CVE-2026-42786
Description
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.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
banditHex | >= 0.5.0, < 1.11.0 | 1.11.0 |
Affected products
2Patches
Vulnerability mechanics
References
6- github.com/advisories/GHSA-pf94-94m9-536pghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-42786ghsaADVISORY
- cna.erlef.org/cves/CVE-2026-42786.htmlnvdWEB
- github.com/mtrudel/bandit/commit/21612c7c7b1ce43eccd36d3af3a2299d23513667nvdWEB
- github.com/mtrudel/bandit/security/advisories/GHSA-pf94-94m9-536pnvdWEB
- osv.dev/vulnerability/EEF-CVE-2026-42786nvdWEB
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