CVE-2021-43977Network attack vector

Browser script execution via undisclosed webmail flaw

Published Nov 17, 2021 · Updated Aug 4, 2024

Cross-site scripting in SmarterTools SmarterMail 16.x through 100.x before 100.0.7803 allows remote attackers to run script in a user's browser. The public CVE record and disclosure identify the webmail frontend but do not disclose the affected request, parameter, or output-encoding failure. Exploitation requires user interaction; successful script execution can read or alter data available to the victim's webmail session.

CVSS severity6.1
Medium
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in SmarterTools SmarterMail 16.x through 100.x before 100.0.7803 allows remote attackers to run script in a user's browser. The public CVE record and disclosure identify the webmail frontend but do not disclose the affected request, parameter, or output-encoding failure. Exploitation requires user interaction; successful script execution can read or alter data available to the victim's webmail session.

The record

CVE
CVE-2021-43977
Published
Nov 17, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 17, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/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.

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Public exploit references

No public exploit references are available in this record.

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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