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CVE-2026-44726— Deno: TLS retry copies stale upgrade hook, risking plaintext traffic

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.

denoland deno是denoland公司的一个JavaScript和TypeScript运行时环境。 denoland deno 2.0.0版本至2.7.8之前版本存在加密问题漏洞，该漏洞源于Node.js TLS兼容层缺陷，当autoSelectFamily启用且首次地址族尝试失败时，连接重试后可能导致TLS客户端以明文传输应用数据。

CVSS 7.4 · High EPSS 0.17% · P7

Possible ATT&CK Techniques 1 AI

T1042

Affected Version Matrix 1

VendorProduct Version RangeStatus
denoland deno >= 2.0.0, < 2.7.8 affected
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I. Basic Information for CVE-2026-44726

Vulnerability Information
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Vulnerability Title
Deno: TLS retry copies stale upgrade hook, risking plaintext traffic
Source: CVE Program / CVE List V5
Vulnerability Description
Deno is a JavaScript, TypeScript, and WebAssembly runtime. From 2.0.0 until 2.7.8, a flaw in Deno's Node.js tls compatibility layer could cause a TLS client to transmit application data in plaintext after a connection retry. When `autoSelectFamily was enabled and the first address-family attempt failed, the socket reinitialization path reused a stale TLS upgrade hook that was bound to the original, failed handle. As a result, the replacement TCP connection was never upgraded to TLS, and any data the application wrote before the secureConnect event travelled over the network unencrypted. A network attacker positioned to cause the initial connection attempt to fail (for example, by dropping IPv6 traffic on a dual-stack host) could deterministically trigger the fallback path and observe or tamper with traffic that the application believed was TLS-protected. This vulnerability is fixed in 2.7.8.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
敏感数据的明文传输
Source: CVE Program / CVE List V5
Vulnerability Title
denoland deno 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
denoland deno是denoland公司的一个JavaScript和TypeScript运行时环境。 denoland deno 2.0.0版本至2.7.8之前版本存在加密问题漏洞，该漏洞源于Node.js TLS兼容层缺陷，当autoSelectFamily启用且首次地址族尝试失败时，连接重试后可能导致TLS客户端以明文传输应用数据。
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 >= 2.0.0, < 2.7.8 -

II. Public POCs for CVE-2026-44726

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III. Intelligence Information for CVE-2026-44726

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Vendor Advisories for CVE-2026-44726 (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-2026-49401 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-2026-49860 5.2 MEDIUM Deno: WebSocket API sandbox bypass via missing post-DNS check
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-319

V. Comments for CVE-2026-44726

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