Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Deno versions before 2.8.1 have a sandbox bypass in the WebSocket API: when a WebSocket connection was opened, the hostname was checked against --deny-net rules but the resolved IP addresses were not re-checked. Code run with --deny-net can use a crafted domain name that passes the hostname check yet resolves to a denied address, reaching hosts the user meant to block. Upgrade to Deno 2.8.1 or later. The source lists no workaround other than avoiding untrusted code with network restrictions.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.2 | Medium | 3.1 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0014, the 3rd percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 15:18 UTC First seen by agentprime
- 31 Oct 2026, 15:18 UTC Confirmed by OSV