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-JS-PHOENIX-17889828
- published8 Jul 2026
- disclosed7 Jul 2026
- creditPJUllrich
Introduced: 7 Jul 2026
NewCVE-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 The official JavaScript client for the Phoenix web framework.
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.