CVE-2021-3734: yourls is vulnerable to Improper Restriction of Rendered UI Layers or Frames

Q: How do I fix CVE-2021-3734?

yourls: upgrade to newer than 1.8.1. Exact commands for each OS are on this page.

Q: Is CVE-2021-3734 being exploited?

CVE-2021-3734 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-3734 affect?

CVE-2021-3734 affects yourls. Severity is high (CVSS 8.8). yourls is vulnerable to Improper Restriction of Rendered UI Layers or Frames

Q: How urgent is CVE-2021-3734?

Priority 44/100. High severity; Public exploit reference

This month

HIGH 8.8UPGRADE

CVE-2021-3734 is a high-severity flaw (CVSS 8.8) affecting yourls. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 65%)
CISA exploited list	No
Weakness	CWE-1021, CWE-352
Published	2021-08-26
Last modified	2026-06-17

Publisher (CNA): huntr.dev · Vendor: yourls

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-08-26 13:15 UTCPublished CVE record published
2026-06-17 04:05 UTCUpdated Record last modified

yourls yourls UPGRADE

Affected: <= 1.8.1

Fixed in: newer than 1.8.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy yourls || rpm -q yourls || yourls --version

2. UPGRADE to newer than 1.8.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade yourls

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade yourls

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-3734?

yourls: upgrade to newer than 1.8.1. Exact commands for each OS are on this page.

Is CVE-2021-3734 being exploited?

CVE-2021-3734 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-3734 affect?

CVE-2021-3734 affects yourls. Severity is high (CVSS 8.8). yourls is vulnerable to Improper Restriction of Rendered UI Layers or Frames

How urgent is CVE-2021-3734?

Priority 44/100. High severity; Public exploit reference

Related CVEs

CVE-2020-27388 MEDIUM 5.4 UPGRADE Multiple Stored Cross Site Scripting (XSS) vulnerabilities exist in the YOURLS Admin Panel, Versions 1.5 - 1.7
CVE-2022-0088 HIGH 7.4 UPGRADE Cross-Site Request Forgery (CSRF) in GitHub repository yourls/yourls prior to 1.8.3.
CVE-2021-3785 MEDIUM 5.4 UPGRADE yourls is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE-2021-3783 MEDIUM 6.1 UPGRADE yourls is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

References

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