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CVE-2026-49860— Deno: WebSocket API sandbox bypass via missing post-DNS check

Quick assessment

Affected
denoland deno
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Deno是Deno组织开源的一个简单、现代且安全的 JavaScript 和 TypeScript 运行环境。 Deno Land Deno 2.8.1之前版本存在服务端请求伪造漏洞，该漏洞源于WebSocket连接时未重新检查解析后的IP地址，可能导致攻击者控制的脚本使用特制域名绕过网络限制。

CVSS 5.2 · Medium EPSS 0.14% · P3

Possible ATT&CK Techniques 1 AI

T1562.001

Affected Version Matrix 1

VendorProduct Version RangeStatus
denoland deno < 2.8.1 affected
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I. Basic Information for CVE-2026-49860

Vulnerability Information
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Vulnerability Title
Deno: WebSocket API sandbox bypass via missing post-DNS check
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
Deno Land Deno 服务端请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Deno是Deno组织开源的一个简单、现代且安全的 JavaScript 和 TypeScript 运行环境。 Deno Land Deno 2.8.1之前版本存在服务端请求伪造漏洞，该漏洞源于WebSocket连接时未重新检查解析后的IP地址，可能导致攻击者控制的脚本使用特制域名绕过网络限制。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
denoland deno < 2.8.1 -

II. Public POCs for CVE-2026-49860

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III. Intelligence Information for CVE-2026-49860

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Vendor Advisories for CVE-2026-49860 (1)

Same Patch Batch · denoland · 2026-06-23 · 10 CVEs total

CVE-2026-49402 8.1 HIGH Deno: Command Injection via spawnSync & spawn on Windows
CVE-2026-49440 7.4 HIGH Deno: Miller-Rabin Primality Test Allows Zero Rounds
CVE-2026-44726 7.4 HIGH Deno: TLS retry copies stale upgrade hook, risking plaintext traffic
CVE-2026-49401 7.3 HIGH Deno Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)
CVE-2026-49411 6.5 MEDIUM Deno Node TCPWrap numeric hostname aliases bypass --deny-net resolved-IP deny checks
CVE-2026-49406 5.5 MEDIUM Deno: BYONM module resolution allows `package.json` main path traversal to bypass `--allow
CVE-2026-49983 5.2 MEDIUM Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with on
CVE-2026-49859 5.2 MEDIUM Deno: `fetch()` API sandbox bypass via missing DNS resolution check
CVE-2026-55517 4.3 MEDIUM Deno: Denial of service via non-ASCII bytes in WebSocket response headers

IV. Related Vulnerabilities

Same product: deno
Same vendor: denoland
Same weakness: CWE-918

V. Comments for CVE-2026-49860

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