Medium severity · published Jun 23, 2026
CVE-2026-49860
Deno: WebSocket API sandbox bypass via missing post-DNS check
5.2
CVSS
0.1%
EPSS
No
On KEV
Description
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, 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. This vulnerability is fixed in 2.8.1.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 3% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
DE
deno · denoland
< 2.8.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-49860
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-49860
Vendor Advisory
https://github.com/denoland/deno/security/advisories/GHSA-83pc-3rw9-qpwj
More from deno
9.8
CVE-2026-32260
Command Injection via incomplete shell metacharacter blocklist in node:child_process (bypass of CVE-2026-27190 fix)
9.8
CVE-2026-27190
Deno has a Command Injection via Incomplete shell metacharacter blocklist in node:child_process
9.8
CVE-2026-22864
Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass
9.8
CVE-2023-33966
Deno missing "--allow-net" permission check for built-in Node modules
9.8
CVE-2023-28445
Deno improperly handles resizable ArrayBuffer