CVE-2026-56811

Home/CVE/Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) a

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Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) a

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.

EPSS 0.00377

EPSS exploitation odds0.38% · top 70%

Schedule remediation

SSVC automatable: yes - attacks can be scripted at scale
⚠ NVD has not scored this CVE yet - manual triage required (common for recent CVEs)

No Sigma yet — build one → YARA rules0

Look this up elsewhere - one-click external pivots

NVD CVE.org CISA Exploit-DB GitHub PoC VulnCheck KEV GreyNoise

▸ How to read a CVE - triage first, then detect and patch

This page is every public fact about CVE-2026-56811, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.

Triage: should I act now? Four signals, and they are not interchangeable:

CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked. EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal. CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score. Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.

How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.

Then what - two workflows:

Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits. PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.

Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).

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Exploitation momentum

2 days of EPSS

stable

Exploitation pressure is steady. This reads the direction and speed of EPSS over time, which can move before EPSS itself peaks or before CISA lists it.

Window

EPSS 0.004 → 0.004 peak 0.004 velocity +0.000

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Severity & exploitation scoring

EPSS exploitation probability

0.38%

Top 70%odds of exploitation in the next 30 days

CVSS metric silhouette

No structured CVSS vector for this CVE. Older entries often have only a numeric base score - the metric breakdown radar requires a full AV:_/AC:_/... vector string published by NVD.

SSVC triage · cisa-vulnrichment

Exploitation

none

Automatable

yes

Tech impact

partial

Lifecycle

07 Jul 2026Published to NVD
08 Jul 2026Last modified

Every entry is a recorded date - NVD publish/modify, CISA KEV add, public exploit disclosure. No inferred events.

Attack path

Full kill chain

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ATT&CK techniques

Techniques this CVE enables. Pills with a solid outline are high confidence - named directly in ATT&CK or Nuclei, or human-curated by CTID; the rest are inferred from the weakness type using MITRE's CVE Mapping Methodology and the CWE → CAPEC chain. Broad, generic-weakness guesses are filtered out. A small N× marks a technique that N independent sources agree on.

T1498.001 · Direct Network Flood T1498.002 · Reflection Amplification T1499 · Endpoint Denial of Service^2× T1499.001 · OS Exhaustion Flood T1499.002 · Service Exhaustion Flood T1499.003 · Application Exhaustion Flood

▤ Build a SIEM detection for these techniques