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GHSA-83pc-3rw9-qpwj
No affected components available
Summary
When a WebSocket connection was opened, Deno checked the destination hostname
against --deny-net rules but did not re-check the IP addresses that hostname
resolved to. An attacker-controlled script could use a specially crafted domain
name that passes the hostname check yet resolves to a denied IP, bypassing the
network restriction entirely.
Impact
Code running under --deny-net could connect to hosts that the user intended
to block. In practice this means network isolation rules — for example,
blocking access to localhost or internal services — could be silently
circumvented by a malicious or compromised dependency.
Deno.connect and fetch() were not affected by this specific issue (a
companion advisory covers fetch()).
Who is affected
Users who:
- run untrusted or third-party code with
deno run, and - rely on
--deny-netto restrict which hosts that code can reach.
If you do not use --deny-net, or if you only run fully trusted code, you are
not affected.
Workaround
No workaround is available short of upgrading. If upgrading immediately is not
possible, avoid granting --allow-net to untrusted code that also has
--deny-net restrictions you depend on for security.
The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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