Auth bypass in Scratchoauth2 Project
CVE-2021-29437
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.
Vulnerability class: Broken Access Control
EPSS: 0.008 (53.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N.
Affected products
- Scratchoauth2_project Scratchoauth2
- Scratchverifier Scratchoauth2 — versions < 9220c2a
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Third Party Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2021-29437?
- CVE-2021-29437 is a high-severity vulnerability in Scratchoauth2 Project, classified under Incorrect Authorization. CVSS score: 8.0/10. Published 2021-04-13.
- How severe is CVE-2021-29437?
- High severity. CVSS v3 base score is 8.0 out of 10.