How severe is CVE-2021-42053?

CVE-2021-42053 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-42053?

CVE-2021-42053 affects the following packages: django-unicorn (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2021-42053?

Update django-unicorn to 0.36.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-42053 is resolved across your whole dependency graph.

How do I detect CVE-2021-42053 in my PyPI dependencies?

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

How do I mitigate CVE-2021-42053 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-2021-42053 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2021-42053, including 1 documented proof-of-concept exploit on Exploit-DB and 1 in-the-wild exploitation 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-2021-42053?

CVE-2021-42053 has an EPSS (Exploit Prediction Scoring System) score of 2.5%, placing it in the 85th 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-2021-42053?

CVE-2021-42053 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-2021-42053 published, and has it been updated?

CVE-2021-42053 was published on October 7, 2021 and was last updated on October 20, 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-2021-42053 — django-unicorn

MEDIUMFix: adamghill/django-unicorn#288

CVE-2021-42053 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in django-unicorn. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for django-unicorn — see the affected versions and patch details below.

Cross-site scripting in Unicorn framework

Also known asGHSA-c87f-fq5g-63r2PYSEC-2021-357

Published

Oct 7, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

2 known

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

2.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs85th percentile — riskier than 85% 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

🐍django-unicorn

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

The Unicorn framework through 0.35.3 for Django allows XSS via component.name.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`django-unicorn`	all versions	0.36.0`pip install --upgrade 'django-unicorn==0.36.0'`

Affected Products

1 product · 1 configurations

Application

unicorndjango-unicorn

≤ 0.35.3

range

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-50393webappspython

django-unicorn 0.35.3 - Stored Cross-Site Scripting (XSS)

by Raven Security Associates · Oct 8, 2021

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 django-unicorn, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update django-unicorn to 0.36.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-42053 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

The Unicorn framework through 0.35.3 for Django allows XSS via component.name.

O3 Security · Impact-Aware SCA

Is CVE-2021-42053 in your dependencies?

Find it across PyPI, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

5.4/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

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

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No Nuclei template or Metasploit module yet. 2 public proof-of-concept references are listed on this page.

Timeline

Disclosed

Oct 7, 2021

First exploit

Oct 8, 2021

1 day after disclosure — rapid exploitation

Last updated

Oct 20, 2026

Identifiers

CVE-2021-42053

GHSA-c87f-fq5g-63r2

PYSEC-2021-357

References

Advisorynvd.nist.gov · CVE 2021 42053 Advisorygithub.com · GHSA c87f fq5g 63r2 Fixgithub.com · 0.35.3...0.36.0 Fixgithub.com · files Webgithub.com Webgithub.com · aa5b9835d946bd9893ef02e556859e3ea62cc5e2 Webgithub.com · PYSEC 2021 357.yaml Packagegithub.com · django unicorn Evidencepacketstormsecurity.com · django unicorn 0.35.3 Cross Site Scripting

Related vulnerabilities

Also affects django-unicorn

This CVE is medium severity; 3 of 3 other CVEs affecting django-unicorn are rated as high or higher (top: critical).

CVE-2026-31815CVE-2025-24370CVE-2021-42134

Same weakness: CWE-79

This CVE is medium severity; 3 of 5 other CVEs with CWE-79 are rated as high or higher (top: high).

CVE-2026-126075CVE-2026-126063CVE-2026-110802CVE-2026-123364CVE-2026-118670Browse all CWE-79

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 20, 2026