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No exploitation reported

CVE-2021-43437

No exploitation reported by the sources we read.

  • Published2021-12-20
  • WeaknessCWE-74

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In sourcecodetester Engineers Online Portal as of 10-21-21, an attacker can manipulate the Host header as seen by the web application and cause the application to behave in unexpected ways. Very often multiple websites are hosted on the same IP address. This is where the Host Header comes in. This header specifies which website should process the HTTP request. The web server uses the value of this header to dispatch the request to the specified website. Each website hosted on the same IP address is called a virtual host. And It's possible to send requests with arbitrary Host Headers to the first virtual host.

Timeline

dates in UTC
  1. 2021-12-2020:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-43437?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-43437?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Engineers online portal project engineers online portal
BranchAffectedFixed in
1.0= 1.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVSS 3.18.8read 2026-10-23
  • NVDCVSS 2.06.8read 2026-10-23
  • NVDweakness (CWE)CWE-74read 2026-10-23
  • FIRST EPSSEPSS score1.3 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
2021-12-20
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-43437?

In sourcecodetester Engineers Online Portal as of 10-21-21, an attacker can manipulate the Host header as seen by the web application and cause the application to behave in unexpected ways. Very often multiple websites are hosted on the same IP address. This is where the Host Header comes in. This header specifies which website should process the HTTP request. The web server uses the value of this header to dispatch the request to the specified website. Each website hosted on the same IP address is called a virtual host. And It's possible to send requests with arbitrary Host Headers to the first virtual host.

Is CVE-2021-43437 actively exploited?

Active exploitation of CVE-2021-43437 has not been confirmed. Its EPSS score was 1.3% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-43437?

CVE-2021-43437 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

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