CVE-2020-36941Public exploitNetwork attack vector

Spreadsheet formula execution via unfiltered server headers

Published Jan 27, 2026 · Updated Jan 27, 2026

CSV injection in guelfoweb Knockpy 4.1.1 allows remote attackers to place spreadsheet formulas in CSV reports through crafted HTTP Server headers. Knockpy appends the unfiltered Server header to subdomain_csv_list, and save_report.py concatenates each item directly into CSV output without neutralizing formula prefixes. Exploitation requires scanning an attacker-controlled host with CSV output enabled and opening the resulting report in a spreadsheet application, where the formula executes in the user's context.

CVSS severity5.3
Medium
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSV injection in guelfoweb Knockpy 4.1.1 allows remote attackers to place spreadsheet formulas in CSV reports through crafted HTTP Server headers. Knockpy appends the unfiltered Server header to subdomain_csv_list, and save_report.py concatenates each item directly into CSV output without neutralizing formula prefixes. Exploitation requires scanning an attacker-controlled host with CSV output enabled and opening the resulting report in a spreadsheet application, where the formula executes in the user's context.

The record

CVE
CVE-2020-36941
Published
Jan 27, 2026
Updated
Jan 27, 2026
Vendor
guelfoweb
Product
Knockpy
Classifications
CWE-1236, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

guelfoweb · Knockpyversion=4.1.1

Published CVSS scores

9.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1236Improper Neutralization of Formula Elements in a CSV File
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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