How severe is CVE-2014-3146?

CVE-2014-3146 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2014-3146?

CVE-2014-3146 affects the following packages: lxml (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2014-3146?

Update lxml to 3.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2014-3146 is resolved across your whole dependency graph.

How do I detect CVE-2014-3146 in my PyPI dependencies?

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

How do I mitigate CVE-2014-3146 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2014-3146 actively exploited in the wild?

Yes. There are 4 known exploit references for CVE-2014-3146, including 1 documented proof-of-concept exploit on Exploit-DB and 3 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2014-3146?

CVE-2014-3146 has an EPSS (Exploit Prediction Scoring System) score of 6.3%, placing it in the 94th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2014-3146?

CVE-2014-3146 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2014-3146 published, and has it been updated?

CVE-2014-3146 was published on May 14, 2014 and was last updated on April 16, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2014-3146 — lxml

MEDIUMFix: lxml/lxml#273

CVE-2014-3146 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in lxml. 4 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for lxml — see the affected versions and patch details below.

lxml Cross-site Scripting Via Control Characters

Also known asGHSA-57qw-cc2g-pv5pPYSEC-2014-9

Published

May 14, 2014

Updated

Apr 16, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

4 known

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2014-3146.

EPSS Exploitation Probability

via FIRST.org ↗

6.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs94th percentile — riskier than 94% of all scored CVEsHighest risk

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

🐍lxml

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

Description

Incomplete blacklist vulnerability in the lxml.html.clean module in lxml before 3.3.5 allows remote attackers to conduct cross-site scripting (XSS) attacks via control characters in the link scheme to the clean_html function.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`lxml`	all versions	3.3.5`pip install --upgrade 'lxml==3.3.5'`

Affected Products

1 product · 95 configurations

Application

lxmllxml

≤ 3.3.4

75 versions

0.50.5.10.60.70.80.90.9.10.9.21.01.0.11.0.21.0.3

Exploits & PoCs

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

EDB-39155remotelinux✓ Verified

lxml - 'clean_html' Security Bypass

by Maksim Kochkin · Apr 15, 2014

Exploit-DB Source

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lxml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update lxml to 3.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2014-3146 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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