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CRITICAL severity

CVE-2021-23654 — html-to-csv

CRITICAL

CVE-2021-23654 is a critical-severity (CVSS 9.8) CWE-1236 vulnerability in html-to-csv. 2 public exploit references exist, so weaponization risk is real. No vendor fix is recorded yet; mitigation options are listed below.

Improper Neutralization of Formula Elements in a CSV File in html-2-csv

Also known asGHSA-fwf6-rw69-hhj4PYSEC-2021-866SNYK-PYTHON-HTMLTOCSV-1582784
Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
2 known
Exploitation data as of Oct 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk
0.68%1.04%1.39%1.75%1.2%1.2%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-23654 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐍html-to-csv

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

This affects all versions of package html-to-csv. When there is a formula embedded in a HTML page, it gets accepted without any validation and the same would be pushed while converting it into a CSV file. Through this a malicious actor can embed or generate a malicious link or execute commands via CSV files.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
🐍PyPIhtml-to-csvall versionsNo fix

Affected Products

1 product · 1 configurations
Application
html-to-csvhtml-to-csv_project
≤ 0.1.3
range
Exploits & PoCs
2

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

This affects all versions of package html-to-csv. When there is a formul…

snyk.ioNVDDec 2021

This affects all versions of package html-to-csv. When there is a formul…

github.comNVDDec 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 html-to-csv, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    No patched version of html-to-csv has shipped for CVE-2021-23654 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  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

This affects all versions of package html-to-csv. When there is a formula embedded in a HTML page, it gets accepted without any validation and the same would be pushed while converting it into a CSV file. Through this a malicious actor can embed or generate a malicious link or execute commands via CSV files.
O3 Security · Impact-Aware SCA

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CVE-2021-23654: html-to-csv (Critical 9.8)