phoenixframework/phoenix · Security
Phoenix: Unbounded channel joins per transport enables DoS over few connections
- GHSA ID
- GHSA-6983-jfq8-485w
- CVE ID
- CVE-2026-56811
- Severity
- high
- Published
- Updated
- CVSS
- 7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CVSS v3
- 7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CVSS v4
- 8.7 · 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
Description
Summary
Phoenix transports do not limit the number of channels in a given connection, making it easy to spawn hundreds of thousands of processes over a single connection, and, eventually reaching the max processes VM limit. The solution is to limit the number of channels per transport, so an attacker needs to start new HTTP/WebSocket connections, allowing third-party services to apply rate limits and intervene more easily.
Impact
An unauthenticated remote attacker can cause a denial of service against any Phoenix app that exposes LongPoll/WebSocket transports.
CWEs
- CWE-770 · Allocation of Resources Without Limits or Throttling
References
- https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w ↗
- https://nvd.nist.gov/vuln/detail/CVE-2026-56811 ↗
- https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a ↗
- https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1 ↗
- https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218 ↗
- https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e ↗
- https://cna.erlef.org/cves/CVE-2026-56811.html ↗
- https://osv.dev/vulnerability/EEF-CVE-2026-56811 ↗
- https://github.com/advisories/GHSA-6983-jfq8-485w ↗