CVE-2021-20101Public exploitNetwork attack vector

User redirection via unvalidated Host header

Published Jun 29, 2021 · Updated Aug 3, 2024

HTTP host header injection in Laymance Technologies LLC MachForm before 16 allows remote attackers to redirect users through crafted requests. The export_entries.php path and other redirect paths construct Location responses from the unvalidated Host header. Exploitation requires a caching proxy and victim interaction; poisoned responses can send users to an attacker-controlled domain.

CVSS severity4.3
Medium
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP host header injection in Laymance Technologies LLC MachForm before 16 allows remote attackers to redirect users through crafted requests. The export_entries.php path and other redirect paths construct Location responses from the unvalidated Host header. Exploitation requires a caching proxy and victim interaction; poisoned responses can send users to an attacker-controlled domain.

The record

CVE
CVE-2021-20101
Published
Jun 29, 2021
Updated
Aug 3, 2024
Vendor
Laymance Technologies LLC
Product
MachForm
Classifications
CWE-20, CWE-74, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=All versions prior to version 16

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Laymance Technologies LLC · MachFormversion=All versions prior to version 16

Published CVSS scores

4.3Tenable ResearchCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A: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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1190Exploit Public-Facing Application

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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