Topic presence-sync denial via inherited-property confusion
Published Jul 7, 2026 · Updated Jul 7, 2026
Denial of service in Phoenix Presence before 1.5.15, 1.6.17, 1.7.24, or 1.8.9 allows remote authenticated users to freeze topic sync. Presence.syncState and Presence.syncDiff treat inherited Object.prototype members as existing state, then call metas.map on undefined and throw an uncaught TypeError. Exploitation requires a Phoenix.Presence application to track a client-influenced key; repeated server pushes keep synchronization broken for viewers of that topic until the attacker leaves.
Summary
What happened
Denial of service in Phoenix Presence before 1.5.15, 1.6.17, 1.7.24, or 1.8.9 allows remote authenticated users to freeze topic sync. Presence.syncState and Presence.syncDiff treat inherited Object.prototype members as existing state, then call metas.map on undefined and throw an uncaught TypeError. Exploitation requires a Phoenix.Presence application to track a client-influenced key; repeated server pushes keep synchronization broken for viewers of that topic until the attacker leaves.
The record
- CVE
- CVE-2026-56812
- Published
- Jul 7, 2026
- Updated
- Jul 7, 2026
- Vendor
- Phoenix Framework
- Product
- Phoenix
- Classifications
- CWE-754, CAPEC-153, T1499
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 7, 2026CVE publishedPublication date reported by the CVE source.
- Jul 7, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.2.0-rc.0 <1.5.15
- Affected versionversion=1.6.0-rc.0 <1.6.17
- Affected versionversion=1.7.0-rc.0 <1.7.24
- Affected versionversion=1.8.0-rc.0 <1.8.9
- Affected versionversion=2270aaf21bd02c6a6a1022820564efb605a97655 <* changes=[{"at":"7f7b971c1ea0994e3fbd1c11ddb05e780bd38ad8","status":"unaffected"},{"at":"89a1c4be161e436241e12b2378a719904b9bd96f","status":"unaffected"},{"at":"b90b22521465ece00eb5a19d5aa2b9465b209c85","status":"unaffected"},{"at":"beffc4da1e787e572121f68902c63daf4fe7d9c2","status":"unaffected"}]
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream presence-key collision proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo