CVE-2026-56811Network attack vector

Unauthenticated service interruption via unbounded channel joins

Published Jul 7, 2026 · Updated Jul 7, 2026

Resource exhaustion in Phoenix allows remote attackers to interrupt service by joining unbounded channels over a reachable transport. Phoenix.Socket handle_in/4 accepts every phx_join message without limiting channels per transport and starts a persistent channel process for each join. An unauthenticated client needs a mounted socket with a reachable WebSocket or LongPoll channel; enough joins exhaust the BEAM process table and deny traffic across the node.

CVSS severity8.7
High
EPSS probability0.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Phoenix allows remote attackers to interrupt service by joining unbounded channels over a reachable transport. Phoenix.Socket handle_in/4 accepts every phx_join message without limiting channels per transport and starts a persistent channel process for each join. An unauthenticated client needs a mounted socket with a reachable WebSocket or LongPoll channel; enough joins exhaust the BEAM process table and deny traffic across the node.

The record

CVE
CVE-2026-56811
Published
Jul 7, 2026
Updated
Jul 7, 2026
Vendor
Phoenix Framework
Product
Phoenix
Classifications
CWE-770, CAPEC-130, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 7, 2026CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. Affected versionversion=0.11.0 <1.5.15
  2. Affected versionversion=14a297e88023cb280a577962a49a0bbdeef9f4eb <* changes=[{"at":"c498ba8cf49f6accbbd0c643a5340b58db891218","status":"unaffected"},{"at":"d19ca0a8d9f82c130b7ed339b9f033433e2dea5e","status":"unaffected"},{"at":"a612100cd8a4279091abc1a2ef8fb98a6d01c0a1","status":"unaffected"},{"at":"16e295d2fccab185d1292322e2bee5d46c725c8a","status":"unaffected"}]
  3. Affected versionversion=1.6.0-rc.0 <1.6.17
  4. Affected versionversion=1.7.0-rc.0 <1.7.24
  5. Affected versionversion=1.8.0-rc.0 <1.8.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Phoenix Framework · Phoenixversion=0.11.0 <1.5.15; version=14a297e88023cb280a577962a49a0bbdeef9f4eb <* changes=[{"at":"c498ba8cf49f6accbbd0c643a5340b58db891218","status":"unaffected"},{"at":"d19ca0a8d9f82c130b7ed339b9f033433e2dea5e","status":"unaffected"},{"at":"a612100cd8a4279091abc1a2ef8fb98a6d01c0a1","status":"unaffected"},{"at":"16e295d2fccab185d1292322e2bee5d46c725c8a","status":"unaffected"}]; version=1.6.0-rc.0 <1.6.17; version=1.7.0-rc.0 <1.7.24; version=1.8.0-rc.0 <1.8.9

Published CVSS scores

8.7Erlang Ecosystem FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
CAPEC-130Excessive Allocation
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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