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CVE-2026-72691— OpenSignLabs opensignserver - Authentication Bypass

Quick assessment

Affected
OpenSignLabs opensignserver
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

OpenSignLabs OpenSign是OpenSignLabs组织的一款数字文档签名解决方案。 OpenSignLabs OpenSign 2.37.0及之前版本存在授权问题漏洞，该漏洞源于getsignedurl Parse云函数在提供docId参数时跳过isAuthenticated检查，可能导致未经身份验证的远程攻击者为任意存储文件生成MASTER_KEY签名的文件访问令牌。

CVSS 7.5 · High EPSS 0.65% · P49

Affected Version Matrix 1

VendorProduct Version RangeStatus
OpenSignLabs opensignserver ≤ 2.37.0 affected
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I. Basic Information for CVE-2026-72691

Vulnerability Information
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Vulnerability Title
OpenSignLabs opensignserver - Authentication Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
An authentication bypass vulnerability in OpenSignLabs opensignserver through 2.37.0 allows an unauthenticated remote attacker to mint MASTER_KEY-signed file access tokens for arbitrary stored files via the getsignedurl Parse cloud function. The function skips its isAuthenticated check whenever any docId parameter is supplied, even one corresponding to no real document, allowing the authentication gate to be bypassed by supplying an arbitrary string as docId.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
使用候选路径或通道进行的认证绕过
Source: CVE Program / CVE List V5
Vulnerability Title
OpenSignLabs OpenSign 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OpenSignLabs OpenSign是OpenSignLabs组织的一款数字文档签名解决方案。 OpenSignLabs OpenSign 2.37.0及之前版本存在授权问题漏洞，该漏洞源于getsignedurl Parse云函数在提供docId参数时跳过isAuthenticated检查，可能导致未经身份验证的远程攻击者为任意存储文件生成MASTER_KEY签名的文件访问令牌。
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
OpenSignLabs opensignserver 0 ~ 2.37.0 -

II. Public POCs for CVE-2026-72691

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Reproduction recording is a Pro+ exclusive
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claude_code · 8945 chars
GitHub 复现环境（可 clone 直接跑）
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
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Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-72691

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Vendor Pages for CVE-2026-72691 (1)

Same Patch Batch · OpenSignLabs · 2026-08-10 · 4 CVEs total

CVE-2026-72688 7.5 HIGH OpenSignLabs opensignserver - Missing Authentication for Critical Function
CVE-2026-72689 7.5 HIGH OpenSignLabs opensignserver - Broken Object Level Authorization
CVE-2026-72692 7.5 HIGH OpenSignLabs opensignserver - Missing Authorization

IV. Related Vulnerabilities

Same product: opensignserver
Same vendor: OpenSignLabs
Same weakness: CWE-288

V. Comments for CVE-2026-72691

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