CVE-2026-56811 (GCVE-0-2026-56811)
Vulnerability from cvelistv5 – Published: 2026-07-07 15:09 – Updated: 2026-09-24 21:28
VLAI
EPSS
VEX
Title
Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service
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.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-07 16:12 UTC
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| phoenixframework | phoenix |
Affected:
0.11.0 , < 1.5.15
(semver)
Affected: 1.6.0-rc.0 , < 1.6.17 (semver) Affected: 1.7.0-rc.0 , < 1.7.24 (semver) Affected: 1.8.0-rc.0 , < 1.8.9 (semver) cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:* |
||
| phoenixframework | phoenix |
Affected:
14a297e88023cb280a577962a49a0bbdeef9f4eb , < *
(git)
cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:* |
Date Public
2026-07-07 15:09
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-56811",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-07T16:12:27.662417Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-07-07T16:12:37.299Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Phoenix.Socket\u0027"
],
"packageName": "phoenix",
"packageURL": "pkg:hex/phoenix",
"product": "phoenix",
"programFiles": [
"lib/phoenix/socket.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
}
],
"repo": "https://github.com/phoenixframework/phoenix",
"vendor": "phoenixframework",
"versions": [
{
"lessThan": "1.5.15",
"status": "affected",
"version": "0.11.0",
"versionType": "semver"
},
{
"lessThan": "1.6.17",
"status": "affected",
"version": "1.6.0-rc.0",
"versionType": "semver"
},
{
"lessThan": "1.7.24",
"status": "affected",
"version": "1.7.0-rc.0",
"versionType": "semver"
},
{
"lessThan": "1.8.9",
"status": "affected",
"version": "1.8.0-rc.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Phoenix.Socket\u0027"
],
"packageName": "phoenixframework/phoenix",
"packageURL": "pkg:github/phoenixframework/phoenix",
"product": "phoenix",
"programFiles": [
"lib/phoenix/socket.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
}
],
"repo": "https://github.com/phoenixframework/phoenix",
"vendor": "phoenixframework",
"versions": [
{
"changes": [
{
"at": "c498ba8cf49f6accbbd0c643a5340b58db891218",
"status": "unaffected"
},
{
"at": "d19ca0a8d9f82c130b7ed339b9f033433e2dea5e",
"status": "unaffected"
},
{
"at": "a612100cd8a4279091abc1a2ef8fb98a6d01c0a1",
"status": "unaffected"
},
{
"at": "16e295d2fccab185d1292322e2bee5d46c725c8a",
"status": "unaffected"
}
],
"lessThan": "*",
"status": "affected",
"version": "14a297e88023cb280a577962a49a0bbdeef9f4eb",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eThe application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send \u003ccode\u003ephx_join\u003c/code\u003e messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send `phx_join` messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected."
}
],
"value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send phx_join messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.5.15",
"versionStartIncluding": "0.11.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.6.17",
"versionStartIncluding": "1.6.0-rc.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.7.24",
"versionStartIncluding": "1.7.0-rc.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.8.9",
"versionStartIncluding": "1.8.0-rc.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Steffen Deusch"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
},
{
"lang": "en",
"type": "analyst",
"value": "Jos\u00e9 Valim"
}
],
"datePublic": "2026-07-07T15:09:57.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAllocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (\u003ccode\u003ePhoenix.Socket\u003c/code\u003e 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).\u003c/p\u003e\n\u003cp\u003eThis vulnerability is associated with program files \u003ccode\u003elib/phoenix/socket.ex\u003c/code\u003e and program routine \u003ccode\u003e\u0027Elixir.Phoenix.Socket\u0027:handle_in/4\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003ePhoenix transports do not limit the number of channels that a single transport process may join. Every \u003ccode\u003ephx_join\u003c/code\u003e 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 \u003ccode\u003ephx_join\u003c/code\u003e 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.\u003c/p\u003e\n\u003cp\u003eThe fix adds a \u003ccode\u003e:max_channels_per_transport\u003c/code\u003e option (default \u003ccode\u003e100\u003c/code\u003e) 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.\u003c/p\u003e\n\u003cp\u003eThis 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.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "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).\n\nThis vulnerability is associated with program files `lib/phoenix/socket.ex` and program routine `\u0027Elixir.Phoenix.Socket\u0027:handle_in/4`.\n\nPhoenix 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.\n\nThe 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.\n\nThis 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."
}
],
"value": "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).\n\nThis vulnerability is associated with program files lib/phoenix/socket.ex and program routine \u0027Elixir.Phoenix.Socket\u0027:handle_in/4.\n\nPhoenix 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.\n\nThe 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.\n\nThis 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."
}
],
"impacts": [
{
"capecId": "CAPEC-130",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-130 Excessive Allocation"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 8.7,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-770",
"description": "CWE-770 Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-24T21:28:45.227Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w"
},
{
"name": "EEF CNA record for CVE-2026-56811",
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-56811.html"
},
{
"name": "OSV record EEF-CVE-2026-56811",
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811"
},
{
"name": "Introducing commit 14a297e in phoenixframework/phoenix",
"tags": [
"related"
],
"url": "https://github.com/phoenixframework/phoenix/commit/14a297e88023cb280a577962a49a0bbdeef9f4eb"
},
{
"name": "Fix commit c498ba8 in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218"
},
{
"name": "Fix commit d19ca0a in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e"
},
{
"name": "Fix commit a612100 in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1"
},
{
"name": "Fix commit 16e295d in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eFront the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove \u003ccode\u003elongpoll: true\u003c/code\u003e from the \u003ccode\u003esocket\u003c/code\u003e declaration where the LongPoll transport is not required). Lowering the BEAM \u003ccode\u003e+P\u003c/code\u003e maximum process limit does not prevent the exhaustion and can make it easier to trigger.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove `longpoll: true` from the `socket` declaration where the LongPoll transport is not required). Lowering the BEAM `+P` maximum process limit does not prevent the exhaustion and can make it easier to trigger."
}
],
"value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove longpoll: true from the socket declaration where the LongPoll transport is not required). Lowering the BEAM +P maximum process limit does not prevent the exhaustion and can make it easier to trigger."
}
]
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-56811",
"datePublished": "2026-07-07T15:09:57.581Z",
"dateReserved": "2026-06-23T12:29:02.507Z",
"dateUpdated": "2026-09-24T21:28:45.227Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-56811",
"date": "2026-09-27",
"epss": "0.00775",
"percentile": "0.53985"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Phoenix.Socket\u0027"
],
"packageName": "phoenix",
"packageURL": "pkg:hex/phoenix",
"product": "phoenix",
"programFiles": [
"lib/phoenix/socket.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
}
],
"repo": "https://github.com/phoenixframework/phoenix",
"vendor": "phoenixframework",
"versions": [
{
"lessThan": "1.5.15",
"status": "affected",
"version": "0.11.0",
"versionType": "semver"
},
{
"lessThan": "1.6.17",
"status": "affected",
"version": "1.6.0-rc.0",
"versionType": "semver"
},
{
"lessThan": "1.7.24",
"status": "affected",
"version": "1.7.0-rc.0",
"versionType": "semver"
},
{
"lessThan": "1.8.9",
"status": "affected",
"version": "1.8.0-rc.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Phoenix.Socket\u0027"
],
"packageName": "phoenixframework/phoenix",
"packageURL": "pkg:github/phoenixframework/phoenix",
"product": "phoenix",
"programFiles": [
"lib/phoenix/socket.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
}
],
"repo": "https://github.com/phoenixframework/phoenix",
"vendor": "phoenixframework",
"versions": [
{
"changes": [
{
"at": "c498ba8cf49f6accbbd0c643a5340b58db891218",
"status": "unaffected"
},
{
"at": "d19ca0a8d9f82c130b7ed339b9f033433e2dea5e",
"status": "unaffected"
},
{
"at": "a612100cd8a4279091abc1a2ef8fb98a6d01c0a1",
"status": "unaffected"
},
{
"at": "16e295d2fccab185d1292322e2bee5d46c725c8a",
"status": "unaffected"
}
],
"lessThan": "*",
"status": "affected",
"version": "14a297e88023cb280a577962a49a0bbdeef9f4eb",
"versionType": "git"
}
]
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"matchCriteriaId": "3CF8EA55-C063-4742-87ED-53E1998977B5",
"versionEndExcluding": "1.5.15",
"versionStartIncluding": "1.2.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"matchCriteriaId": "809E49A8-D727-4E05-BBF9-F9E34077E4A4",
"versionEndExcluding": "1.6.17",
"versionStartIncluding": "1.6.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"matchCriteriaId": "3257C901-8FC3-4107-95C6-C57F909FFE40",
"versionEndExcluding": "1.7.24",
"versionStartIncluding": "1.7.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"matchCriteriaId": "8F98C1AC-1593-43EB-929A-4D3B7597C9BC",
"versionEndExcluding": "1.8.9",
"versionStartIncluding": "1.8.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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).\n\nThis vulnerability is associated with program files lib/phoenix/socket.ex and program routine \u0027Elixir.Phoenix.Socket\u0027:handle_in/4.\n\nPhoenix 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.\n\nThe 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.\n\nThis 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."
}
],
"id": "CVE-2026-56811",
"lastModified": "2026-09-24T22:17:00.407",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 3.6,
"source": "nvd@nist.gov",
"type": "Primary"
}
],
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 8.7,
"baseSeverity": "HIGH",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-56811",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-07T16:12:27.662417Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-07-07T16:16:40.710",
"references": [
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Mitigation",
"Patch",
"Third Party Advisory"
],
"url": "https://cna.erlef.org/cves/CVE-2026-56811.html"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/phoenixframework/phoenix/commit/14a297e88023cb280a577962a49a0bbdeef9f4eb"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Patch",
"Vendor Advisory"
],
"url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"tags": [
"Mitigation",
"Third Party Advisory"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811"
}
],
"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-770"
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-56811",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-07T16:12:27.662417Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-07-07T16:12:32.451Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Phoenix.Socket\u0027"
],
"packageName": "phoenix",
"packageURL": "pkg:hex/phoenix",
"product": "phoenix",
"programFiles": [
"lib/phoenix/socket.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
}
],
"repo": "https://github.com/phoenixframework/phoenix",
"vendor": "phoenixframework",
"versions": [
{
"lessThan": "1.5.15",
"status": "affected",
"version": "0.11.0",
"versionType": "semver"
},
{
"lessThan": "1.6.17",
"status": "affected",
"version": "1.6.0-rc.0",
"versionType": "semver"
},
{
"lessThan": "1.7.24",
"status": "affected",
"version": "1.7.0-rc.0",
"versionType": "semver"
},
{
"lessThan": "1.8.9",
"status": "affected",
"version": "1.8.0-rc.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Phoenix.Socket\u0027"
],
"packageName": "phoenixframework/phoenix",
"packageURL": "pkg:github/phoenixframework/phoenix",
"product": "phoenix",
"programFiles": [
"lib/phoenix/socket.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
}
],
"repo": "https://github.com/phoenixframework/phoenix",
"vendor": "phoenixframework",
"versions": [
{
"changes": [
{
"at": "c498ba8cf49f6accbbd0c643a5340b58db891218",
"status": "unaffected"
},
{
"at": "d19ca0a8d9f82c130b7ed339b9f033433e2dea5e",
"status": "unaffected"
},
{
"at": "a612100cd8a4279091abc1a2ef8fb98a6d01c0a1",
"status": "unaffected"
},
{
"at": "16e295d2fccab185d1292322e2bee5d46c725c8a",
"status": "unaffected"
}
],
"lessThan": "*",
"status": "affected",
"version": "14a297e88023cb280a577962a49a0bbdeef9f4eb",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eThe application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send \u003ccode\u003ephx_join\u003c/code\u003e messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send `phx_join` messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected."
}
],
"value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send phx_join messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.5.15",
"versionStartIncluding": "0.11.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.6.17",
"versionStartIncluding": "1.6.0-rc.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.7.24",
"versionStartIncluding": "1.7.0-rc.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.8.9",
"versionStartIncluding": "1.8.0-rc.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Steffen Deusch"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
},
{
"lang": "en",
"type": "analyst",
"value": "Jos\u00e9 Valim"
}
],
"datePublic": "2026-07-07T15:09:57.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAllocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (\u003ccode\u003ePhoenix.Socket\u003c/code\u003e 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).\u003c/p\u003e\n\u003cp\u003eThis vulnerability is associated with program files \u003ccode\u003elib/phoenix/socket.ex\u003c/code\u003e and program routine \u003ccode\u003e\u0027Elixir.Phoenix.Socket\u0027:handle_in/4\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003ePhoenix transports do not limit the number of channels that a single transport process may join. Every \u003ccode\u003ephx_join\u003c/code\u003e 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 \u003ccode\u003ephx_join\u003c/code\u003e 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.\u003c/p\u003e\n\u003cp\u003eThe fix adds a \u003ccode\u003e:max_channels_per_transport\u003c/code\u003e option (default \u003ccode\u003e100\u003c/code\u003e) 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.\u003c/p\u003e\n\u003cp\u003eThis 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.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "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).\n\nThis vulnerability is associated with program files `lib/phoenix/socket.ex` and program routine `\u0027Elixir.Phoenix.Socket\u0027:handle_in/4`.\n\nPhoenix 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.\n\nThe 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.\n\nThis 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."
}
],
"value": "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).\n\nThis vulnerability is associated with program files lib/phoenix/socket.ex and program routine \u0027Elixir.Phoenix.Socket\u0027:handle_in/4.\n\nPhoenix 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.\n\nThe 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.\n\nThis 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."
}
],
"impacts": [
{
"capecId": "CAPEC-130",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-130 Excessive Allocation"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 8.7,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-770",
"description": "CWE-770 Allocation of Resources Without Limits or Throttling",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-24T21:28:45.227Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w"
},
{
"name": "EEF CNA record for CVE-2026-56811",
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-56811.html"
},
{
"name": "OSV record EEF-CVE-2026-56811",
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811"
},
{
"name": "Introducing commit 14a297e in phoenixframework/phoenix",
"tags": [
"related"
],
"url": "https://github.com/phoenixframework/phoenix/commit/14a297e88023cb280a577962a49a0bbdeef9f4eb"
},
{
"name": "Fix commit c498ba8 in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218"
},
{
"name": "Fix commit d19ca0a in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e"
},
{
"name": "Fix commit a612100 in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1"
},
{
"name": "Fix commit 16e295d in phoenixframework/phoenix",
"tags": [
"patch"
],
"url": "https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eFront the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove \u003ccode\u003elongpoll: true\u003c/code\u003e from the \u003ccode\u003esocket\u003c/code\u003e declaration where the LongPoll transport is not required). Lowering the BEAM \u003ccode\u003e+P\u003c/code\u003e maximum process limit does not prevent the exhaustion and can make it easier to trigger.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove `longpoll: true` from the `socket` declaration where the LongPoll transport is not required). Lowering the BEAM `+P` maximum process limit does not prevent the exhaustion and can make it easier to trigger."
}
],
"value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove longpoll: true from the socket declaration where the LongPoll transport is not required). Lowering the BEAM +P maximum process limit does not prevent the exhaustion and can make it easier to trigger."
}
]
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-56811",
"datePublished": "2026-07-07T15:09:57.581Z",
"dateReserved": "2026-06-23T12:29:02.507Z",
"dateUpdated": "2026-09-24T21:28:45.227Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…