CVE-2026-56811
Unauthenticated DoS via unlimited Phoenix socket channel joins
Is CVE-2026-56811 being exploited?
Not confirmed. CVE-2026-56811 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.76% probability of exploitation in the next 30 days.
How severe is CVE-2026-56811?
CVE-2026-56811 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-56811?
Yes. A fix has been recorded for CVE-2026-56811. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-56811 affect?
CVE-2026-56811 affects phoenix >=0.11.0 <1.5.15, phoenix >=1.6.0-rc.0 <1.6.17, phoenix >=1.7.0-rc.0 <1.7.24, phoenix >=1.8.0-rc.0 <1.8.9. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-56811?
Upgrade to fixed Phoenix versions or set :max_channels_per_transport (default 100).
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated attacker can spawn unbounded channel processes over one WebSocket/LongPoll, exhausting BEAM process table and causing node-wide denial of service.
Immediate action required
- affected>= 0.11.0 and < 1.5.15
- affected>= 1.6.0-rc.0 and < 1.6.17
- affected>= 1.7.0-rc.0 and < 1.7.24
- affected>= 1.8.0-rc.0 and < 1.8.9
- affected>= 14a297e88023cb280a577962a49a0bbdeef9f4eb and < *
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.