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CVE-2023-40021

18
FAUCET Score

CVE-2023-40021 is a timing attack vulnerability in Oppia, an online learning platform, affecting versions prior to 3.3.2-hotfix-2. The vulnerability arises from the insecure comparison of CSRF tokens, allowing an attacker to brute-force the token character by character. This medium-severity flaw (CVSS 5.3) requires user interaction (UI:R) and high attack complexity (AC:H), but successful exploitation could lead to high integrity impact (I:H), enabling an attacker to perform privileged actions on behalf of a logged-in user. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.1.0, < 3.3.2CPE matchmatch criteria
cpe:2.3:a:oppia:oppia:*:*:*:*:*:*:*:*
3.3.2CPE matchmatch criteria
cpe:2.3:a:oppia:oppia:3.3.2:-:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
1.6
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.65%
Probability of exploitation in next 30 days
EPSS Percentile
47.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0065 is in the 62nd percentile among its peer group of 707 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.2 Bluesky, 0.0 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.2 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / oppia/oppia/blob/3a05c3558a292f3db9e658e60e708c266c003fd0/core/controllers/base.py
Product
github.com / oppia/oppia/commit/b89bf808378c1236874b5797a7bda32c77b4af23
Patch
github.com / oppia/oppia/pull/18769
Patch
github.com / oppia/oppia/security/advisories/GHSA-49jp-pjc3-2532
ExploitVendor Advisory