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CVE-2021-29437— Account compromise by man-in-the-middle attack

Quick assessment

Affected
ScratchVerifier ScratchOAuth2
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.

Kenny2github ScratchOAuth2是Kenny2github开源的一个应用软件。验证Scratch帐户是否真实，以用于授权或识别。 ScratchOAuth2 存在安全漏洞，该漏洞源于任何用户可以访问和修改的与scratchoauth2相关的数据都可以由第三方读取和修改。

CVSS 8.0 · High EPSS 0.81% · P54
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I. Basic Information for CVE-2021-29437

Vulnerability Information
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Vulnerability Title
Account compromise by man-in-the-middle attack
Source: CVE Program / CVE List V5
Vulnerability Description
ScratchOAuth2 is an Oauth implementation for Scratch. Any ScratchOAuth2-related data normally accessible and modifiable by a user can be read and modified by a third party. 1. Scratch user visits 3rd party site. 2. 3rd party site asks user for Scratch username. 3. 3rd party site pretends to be user and gets login code from ScratchOAuth2. 4. 3rd party site gives code to user and instructs them to post it on their profile. 5. User posts code on their profile, not knowing it is a ScratchOAuth2 login code. 6. 3rd party site completes login with ScratchOAuth2. 7. 3rd party site has full access to anything the user could do if they directly logged in. See referenced GitHub security advisory for patch notes and workarounds.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Kenny2github ScratchOAuth2 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Kenny2github ScratchOAuth2是Kenny2github开源的一个应用软件。验证Scratch帐户是否真实，以用于授权或识别。 ScratchOAuth2 存在安全漏洞，该漏洞源于任何用户可以访问和修改的与scratchoauth2相关的数据都可以由第三方读取和修改。
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
ScratchVerifier ScratchOAuth2 < 9220c2a -

II. Public POCs for CVE-2021-29437

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 15357 chars
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
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POC zip download
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III. Intelligence Information for CVE-2021-29437

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Patches & Fixes for CVE-2021-29437 (1)

Vendor Advisories for CVE-2021-29437 (1)

IV. Related Vulnerabilities

Same vendor: ScratchVerifier
Same weakness: CWE-863

V. Comments for CVE-2021-29437

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