What is CVE-2021-3734?

CVE-2021-3734 is a high-severity vulnerability in Yourls, classified under Improper Restriction of Rendered UI Layers or Frames (Clickjacking). CVSS score: 8.8/10. Published 2021-08-26.

How severe is CVE-2021-3734?

High severity. CVSS v3 base score is 8.8 out of 10.

CSRF in Yourls

CVE-2021-3734

yourls is vulnerable to Improper Restriction of Rendered UI Layers or Frames

Published 2021-08-26 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.004 (32.3th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 32nd percentile — 32.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Yourls
Yourls Yourls/yourls — versions unspecified

Weakness classification (CWE)

References

huntr.dev/bounties/dd2e2dbe-efe5-49ec-be11-7a7e7c41debd (Exploit, Third Party Advisory, Issue Tracking)
github.com/yourls/yourls/commit/0a70acdcfb5fcbc63dbc5750018d608288eba3fe (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3734?: CVE-2021-3734 is a high-severity vulnerability in Yourls, classified under Improper Restriction of Rendered UI Layers or Frames (Clickjacking). CVSS score: 8.8/10. Published 2021-08-26.
How severe is CVE-2021-3734?: High severity. CVSS v3 base score is 8.8 out of 10.