CVE-2020-18671Public exploitNetwork attack vector

Browser script execution via unescaped SMTP configuration

Published Jun 24, 2021 · Updated Aug 4, 2024

Stored XSS in Roundcube Mail 1.4.4 and earlier allows remote attackers to execute JavaScript through SMTP installer settings. The installer/test.php SMTP test page directly renders attacker-controlled configuration values outside the html_inputfield escaping path. Exploitation requires the installer to remain web-accessible and a user to open its SMTP test step, exposing that browser session to script execution.

CVSS severity5.4
Medium
EPSS probability0.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Roundcube Mail 1.4.4 and earlier allows remote attackers to execute JavaScript through SMTP installer settings. The installer/test.php SMTP test page directly renders attacker-controlled configuration values outside the html_inputfield escaping path. Exploitation requires the installer to remain web-accessible and a user to open its SMTP test step, exposing that browser session to script execution.

The record

CVE
CVE-2020-18671
Published
Jun 24, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Jun 24, 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 privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

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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