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TI-2026-40964 Aliases CVE-2026-56811GHSA-6983-jfq8-485w

Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service

Priority MEDIUM 45CWE-770Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-770.

Summary

Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll). This vulnerability is associated with program files lib/phoenix/socket.ex and program routine 'Elixir.Phoenix.Socket':handle_in/4. Phoenix transports do not limit the number of channels that a single transport process may join. Every phx_join message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of phx_join messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it. The fix adds a :max_channels_per_transport option (default 100) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them. This issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00775 56th percentileScored 2026-11-07
Fix Fixed phoenix (phoenixframework): 1.5.15, 1.6.17, 1.7.24 +1phoenix (Hex): 1.5.15, 1.6.17, 1.7.24 +1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
phoenixframeworkphoenix0.11.0 to before 1.5.15; 1.6.0-rc.0 to before 1.6.17; 1.7.0-rc.0 to before 1.7.24; 1.8.0-rc.0 to before 1.8.91.5.15, 1.6.17, 1.7.24, 1.8.9Patch availableCNA
—phoenix (Hex)0.11.0 to before 1.5.151.5.15Patch availableGHSA-6983-jfq8-485w
—phoenix (Hex)1.6.0-rc.0 to before 1.6.171.6.17Patch availableGHSA-6983-jfq8-485w
—phoenix (Hex)1.7.0-rc.0 to before 1.7.241.7.24Patch availableGHSA-6983-jfq8-485w
—phoenix (Hex)1.8.0-rc.0 to before 1.8.91.8.9Patch availableGHSA-6983-jfq8-485w
  • phoenix Vendorphoenixframework Affected 0.11.0 to before 1.5.15; 1.6.0-rc.0 to before 1.6.17; 1.7.0-rc.0 to before 1.7.24; 1.8.0-rc.0 to before 1.8.9 Fixed in 1.5.15, 1.6.17, 1.7.24, 1.8.9 Patch available CNA
  • phoenix (Hex) Vendor— Affected 0.11.0 to before 1.5.15 Fixed in 1.5.15 Patch available GHSA-6983-jfq8-485w
  • phoenix (Hex) Vendor— Affected 1.6.0-rc.0 to before 1.6.17 Fixed in 1.6.17 Patch available GHSA-6983-jfq8-485w
  • phoenix (Hex) Vendor— Affected 1.7.0-rc.0 to before 1.7.24 Fixed in 1.7.24 Patch available GHSA-6983-jfq8-485w
  • phoenix (Hex) Vendor— Affected 1.8.0-rc.0 to before 1.8.9 Fixed in 1.8.9 Patch available GHSA-6983-jfq8-485w

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*1.2.0 to before 1.5.15; 1.6.0 to before 1.6.17; 1.7.0 to before 1.7.24; 1.8.0 to before 1.8.9Vulnerablephoenixframework
  • cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:* Versions 1.2.0 to before 1.5.15; 1.6.0 to before 1.6.17; 1.7.0 to before 1.7.24; 1.8.0 to before 1.8.9 Vulnerable ·phoenixframework

Remediation

  • Fix · CNA phoenix (phoenixframework) Fixed in 1.5.15, 1.6.17, 1.7.24, 1.8.9
  • Fix · GHSA-6983-jfq8-485w phoenix (Hex) Fixed in 1.5.15 Advisory →
  • Fix · GHSA-6983-jfq8-485w phoenix (Hex) Fixed in 1.6.17 Advisory →
  • Fix · GHSA-6983-jfq8-485w phoenix (Hex) Fixed in 1.7.24 Advisory →
  • Fix · GHSA-6983-jfq8-485w phoenix (Hex) Fixed in 1.8.9 Advisory →

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    phoenixframework phoenix 1.5.15, 1.6.17 and 2 more versions

    2 records Highest priority Priority MEDIUM 2 MEDIUM

    Other records, highest priority first

    • TI-2026-40965 Improper check for unusual conditions in phoenixframework phoenixPriority MEDIUM 61
    Show all 2 records →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-56811
  2. 2026-10-03 Alias added: GHSA-6983-jfq8-485w

References

Patch 6

Advisory 2

Other 2

  • TI-2026-40965 Improper check for unusual conditions in phoenixframework phoenix CVSS 4.0MEDIUM 6.3
  • TI-2022-20955 socket/transport.ex in Phoenix before 1.6.14 mishandles check_origin wildcarding. CVSS 3.1HIGH 7.5
  • TI-2017-14495 The Phoenix Framework versions 1.0.0 through 1.0.4, 1.1.0 through 1.1.6, 1.2.0, 1.2.2 and… CVSS 3.0MEDIUM 6.1

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences