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CVE-2026-3706— mkj Dropbear S Range Check curve25519.c unpackneg signature verification

Quick assessment

Affected
mkj Dropbear
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.

dropbear是Matt Johnston个人开发者的一个应用程序。 dropbear 2025.89及之前版本存在数据伪造问题漏洞，该漏洞源于对组件S Range Check的文件src/curve25519.c中函数unpackneg的错误操作，可能导致加密签名验证不当。

CVSS 3.7 · Low EPSS 0.19% · P8
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I. Basic Information for CVE-2026-3706

Vulnerability Information
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Vulnerability Title
mkj Dropbear S Range Check curve25519.c unpackneg signature verification
Source: CVE Program / CVE List V5
Vulnerability Description
A vulnerability was determined in mkj Dropbear up to 2025.89. Impacted is the function unpackneg of the file src/curve25519.c of the component S Range Check. This manipulation causes improper verification of cryptographic signature. The attack can be initiated remotely. The attack is considered to have high complexity. The exploitability is considered difficult. The actual existence of this vulnerability is currently in question. Patch name: fdec3c90a15447bd538641d85e5a3e3ac981011d. To fix this issue, it is recommended to deploy a patch. The project maintainer explains: "Signature Malleability is not exploitable in SSH protocol. (...) [A] PoC doesn't exist for SSH implementation, but rather it's against the internal API."
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
密码学签名的验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
dropbear 数据伪造问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
dropbear是Matt Johnston个人开发者的一个应用程序。 dropbear 2025.89及之前版本存在数据伪造问题漏洞，该漏洞源于对组件S Range Check的文件src/curve25519.c中函数unpackneg的错误操作，可能导致加密签名验证不当。
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
mkj Dropbear 2025.0 -

II. Public POCs for CVE-2026-3706

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III. Intelligence Information for CVE-2026-3706

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Patches & Fixes for CVE-2026-3706 (2)

Vendor Advisories for CVE-2026-3706 (2)

Proof of Concept for CVE-2026-3706 (2)

News Coverage for CVE-2026-3706 (1)

Vendor Pages for CVE-2026-3706 (1)

IV. Related Vulnerabilities

Same product: Dropbear
Same weakness: CWE-347

V. Comments for CVE-2026-3706

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