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CVE-2021-40978

41
FAUCET Score

CVE-2021-40978 describes a directory traversal vulnerability in the MkDocs 1.2.2 built-in development server, allowing remote attackers to access sensitive information via port 8000. This vulnerability carries a high CVSS score of 7.5, indicating a network-based attack with low complexity and high confidentiality impact, requiring no user interaction or privileges. Although the vendor disputes this finding, its high EPSS and FAUCET Risk Scores suggest a significant threat. Currently, there is no evidence of active exploitation, but Nuclei templates exist for detection, and there is minimal community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
1.2.2CPE matchmatch criteria
cpe:2.3:a:mkdocs:mkdocs:1.2.2:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
14.76%
Probability of exploitation in next 30 days
EPSS Percentile
96.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-40978 · Oct 14, 2021
This CVE's current EPSS score of 0.1476 is in the 95th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

pippatch availablevia ghsa
Product: mkdocsFixed in: 1.2.3

Vendor Advisories (1)

pipGHSA-qh9q-34h6-hcv9high

Directory traversal in mkdocs

Oct 12, 2021

References

github.com / mkdocs/mkdocs
Third Party Advisory
github.com / mkdocs/mkdocs/issues/2601
Issue TrackingThird Party Advisory
github.com / nisdn/CVE-2021-40978
ExploitThird Party Advisory
github.com / nisdn/CVE-2021-40978/issues/1
Issue TrackingThird Party Advisory