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Not in CISA KEV
HIGH severity

CVE-2021-3734 — yourls

HIGHFix: yourls/yourls@0a70acd

CVE-2021-3734 is a high-severity (CVSS 8.8) CWE-1021 vulnerability in yourls/yourls. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Improper Restriction of Rendered UI Layers or Frames in yourls

Also known asGHSA-r6g8-jmj9-g945
Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
1 known
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs35th percentile — riskier than 35% of all scored CVEsHighest risk
0.00%0.30%0.60%0.90%0.2%0.4%May 26Aug 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐘yourls/yourls

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

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

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
🐘Packagistyourls/yourlsall versionsNo fix

Affected Products

1 product · 1 configurations
Application
yourlsyourls
≤ 1.8.1
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

yourls is vulnerable to Improper Restriction of Rendered UI Layers or Fr…

huntr.devNVDSep 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yourls/yourls, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of yourls/yourls for CVE-2021-3734. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

yourls is vulnerable to Improper Restriction of Rendered UI Layers or Frames
O3 Security · Impact-Aware SCA

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CVE-2021-3734: yourls (High 8.8)