Allocation of Resources Without Limits or Throttling Affecting phoenix package, versions >=0.11.0 <1.5.15>=1.6.0-rc.0 <1.6.17>=1.7.0-rc.0 <1.7.24>=1.8.0-rc.0 <1.8.9
Threat Intelligence
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The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-HEX-PHOENIX-17889823
- published8 Jul 2026
- disclosed7 Jul 2026
- creditPJUllrich
Introduced: 7 Jul 2026
CVE-2026-56811 (opens in a new tab)How to fix?
Upgrade phoenix to version 1.5.15, 1.6.17, 1.7.24, 1.8.9 or higher.
Overview
phoenix is a Phoenix is a web development framework written in Elixir which implements the server-side Model View Controller (MVC) pattern. Many of its components and concepts will seem familiar to those of us with experience in other web frameworks like Ruby on Rails or Python's Django.
Phoenix provides the best of both worlds - high developer productivity and high application performance. It also has some interesting new twists like channels for implementing realtime features and pre-compiled templates for blazing speed.
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling through the channel join handling in Phoenix.Socket transport state. An unauthenticated attacker can exhaust VM processes by sending repeated phx_join requests over a single WebSocket or LongPoll connection and creating an unbounded number of channels on one transport. The vulnerable code accepts each join without a per-transport cap, so one client can keep spawning channel processes until the application reaches the Erlang VM’s process limit. This can stall or crash Phoenix apps that expose WebSocket or LongPoll transports, disrupting service for other users.
Notes
- The limit is enforced per transport process, so a single WebSocket or LongPoll connection can only accumulate a bounded number of joined channels.
Phoenix.Socketaccepts a:max_channels_per_transportoption and defaults it to100, so deployments that need a different ceiling have to opt into a non-default value in socket configuration.