CVE-2021-29437 json
Account compromise by man-in-the-middle attack
published 2021-04-13 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-16062
- cvss
- 8.0
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.9%
- EPSS 0.9% chance of exploitation in 30 days, percentile 59%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- scratchoauth2_project scratchoauth2 2021-04-13
Exploit prediction
0.89% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 8.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N |
| NVD | 3.1 | 6.8 | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N |
| NVD | 2.0 | 4.0 | AV:N/AC:H/Au:N/C:P/I:P/A:N |
Affected products
- ScratchVerifier ScratchOAuth2
Classification
- Weakness
-
- CWE-863 Incorrect Authorization
References
Sources
- CVE List CVE-2021-29437
- NVD CVE-2021-29437
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.