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CVE-2026-72688— OpenSignLabs opensignserver - Missing Authentication for Critical Function

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fileupload Parse cloud function未执行会话检查即为任意调用者提供的URL签发MASTER_KEY签名的文件访问令牌，绕过访问控制，可能导致未经身份验证的远程攻击者读取任意存储的文档。

CVSS 7.5 · High EPSS 0.61% · P47

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage

Affected Version Matrix 1

VendorProduct Version RangeStatus
OpenSignLabs opensignserver ≤ 2.37.0 affected
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I. Basic Information for CVE-2026-72688

Vulnerability Information
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Vulnerability Title
OpenSignLabs opensignserver - Missing Authentication for Critical Function
Source: CVE Program / CVE List V5
Vulnerability Description
A missing authentication vulnerability in OpenSignLabs opensignserver through 2.37.0 allows an unauthenticated remote attacker to read arbitrary stored documents via the fileupload Parse cloud function. The function mints MASTER_KEY-signed file access tokens for any caller-supplied URL without performing any session check, defeating the only access control protecting stored contract files.
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
关键功能的认证机制缺失
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fileupload Parse cloud function未执行会话检查即为任意调用者提供的URL签发MASTER_KEY签名的文件访问令牌，绕过访问控制，可能导致未经身份验证的远程攻击者读取任意存储的文档。
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-2026-72688

# 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.
Success marker: VULNERABLE: unauthenticated fileupload minted a MASTER_KEY-signed token; exfiltrated stored document content = "PROOF_6a5883190872ac38" (HTTP 400 without token)
Reproduction recording is a Pro+ exclusive
Watch the full sandbox build + live exploit recording for this CVE. Limited-time ¥499/mo.
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claude_code · 6978 chars
GitHub 复现环境（可 clone 直接跑）
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III. Intelligence Information for CVE-2026-72688

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Vendor Pages for CVE-2026-72688 (1)

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

CVE-2026-72691 7.5 HIGH OpenSignLabs opensignserver - Authentication Bypass
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-306

V. Comments for CVE-2026-72688

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