CVE-2021-29437

Account compromise by man-in-the-middle attack

MEDIUM
6.8
CVSS Score
Published: April 13, 2021 at 06:25 PM UTC
Updated: June 17, 2026 at 03:47 AM UTC
2 products affected across 2 vendorsScratchoauth2ScratchOAuth2

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Severity
MEDIUM6.8
Exploit prediction
EPSS 0.8%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2021-04-13
Affected range stops below 2021-04-13, so it looks safe — our inference, not a vendor statement
v < 9220c2a
Affected range stops below 9220c2a, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-863NVD-CWE-noinfo

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