CVE-2026-56812
Improper Check for Unusual or Exceptional Conditions vulnerability in phoenixframework phoenix (Presence JavaScript client) allows an attacker with ordinary channel access to cause a persistent client-side denial of service against every viewer of a presence channel topic. This vulnerability is associated with program files assets/js/phoenix/presence.js and program routines Presence.syncState and Presence.syncDiff. The Phoenix JavaScript presence client checks whether a presence already exists with a bare truthiness test (state[key]) instead of an own-property check. Presence keys can be attacker-controlled, because applications track presences under a username or id supplied by the client. A user who joins a channel choosing a key that is an Object.prototype member name (__proto__, constructor, toString, hasOwnProperty, and similar) makes that lookup return JavaScript's built-in Object.prototype instead of undefined. Because the prototype is truthy, the code treats it as an existing presence and reads .metas.map(...) off it, which throws an uncaught TypeError. The exception propagates out of the presence message handler, so the local state is never updated and onSync() never fires
Debolezza
Improper Check for Unusual or Exceptional Conditions vulnerability in phoenixframework phoenix (Presence JavaScript client) allows an attacker with ordinary channel access to cause a persistent client-side denial of service against every viewer of a presence channel topic. This vulnerability is associated with program files assets/js/phoenix/presence.js and program routines Presence.syncState and Presence.syncDiff. The Phoenix JavaScript presence client checks whether a presence already exists with a bare truthiness test (state[key]) instead of an own-property check. Presence keys can be attacker-controlled, because applications track presences under a username or id supplied by the client. A user who joins a channel choosing a key that is an Object.prototype member name (__proto__, constructor, toString, hasOwnProperty, and similar) makes that lookup return JavaScript's built-in Object.prototype instead of undefined. Because the prototype is truthy, the code treats it as an existing presence and reads .metas.map(...) off it, which throws an uncaught TypeError. The exception propagates out of the presence message handler, so the local state is never updated and onSync() never fires
Prodotti interessati
- phoenixframework phoenix
Riferimenti
- https://cna.erlef.org/cves/CVE-2026-56812.html
- https://github.com/phoenixframework/phoenix/commit/7f7b971c1ea0994e3fbd1c11ddb05e780bd38ad8
- https://github.com/phoenixframework/phoenix/commit/89a1c4be161e436241e12b2378a719904b9bd96f
- https://github.com/phoenixframework/phoenix/commit/b90b22521465ece00eb5a19d5aa2b9465b209c85
- https://github.com/phoenixframework/phoenix/commit/beffc4da1e787e572121f68902c63daf4fe7d9c2
- https://github.com/phoenixframework/phoenix/security/advisories/GHSA-63mc-hw7g-86rr
Trova il bug prima di un attaccante.
Accedi con GitHub e avvia il tuo primo audit in meno di un minuto. Il piano gratuito non richiede carta di credito.