Improper Check for Unusual or Exceptional Conditions Affecting phoenix package, versions >=1.2.0-rc.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
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-17889827
- published8 Jul 2026
- disclosed7 Jul 2026
- creditPJUllrich
Introduced: 7 Jul 2026
CVE-2026-56812 (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 Improper Check for Unusual or Exceptional Conditions via the syncState and syncDiff presence reconciliation code in assets/js/phoenix/presence.js. An attacker can crash presence updates for every browser viewing a topic by joining with a presence key such as __proto__, constructor, or hasOwnProperty. The vulnerable code stores presence state in plain objects and checks existing entries with state[key], so a prototype-colliding key resolves to an inherited Object.prototype property instead of an actual presence record. When the code then reads .metas.map(...) from that inherited object, it throws an uncaught TypeError, breaking presence synchronization for that channel topic until the attacker leaves.