Is CVE-2020-35730 actively exploited?

Yes. KEV Intelligence tracks CVE-2020-35730 as a known exploited vulnerability. Confidence is confirmed.

What exploitation activity has KEV Intelligence observed?

KEV Intelligence has not yet recorded sensor-observed exploitation attempts for CVE-2020-35730. Our sensors continue to monitor for activity targeting this CVE.

Which versions are affected?

Version-level data is not available; KEV Intelligence tracks Roundcube Webmail.

Yes. CVE-2020-35730 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2020-35730

Webmail Cross-Site Scripting

Roundcube / Webmail

View live feed Monitor via API Watch CVE

Severity: CVSS 6.1 · Medium
Confidence: Confirmed
Exploit status: Exploited in the wild
EPSS: 32.7%
First observed: —
Last observed: —

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2020-35730 is an unauthenticated vulnerability affecting Roundcube Webmail. An XSS issue was discovered in Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10. The attacker can send a...

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.

Who is affected?

Roundcube / Webmail.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

An XSS issue was discovered in Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10

An XSS issue was discovered in Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10.

The attacker can send a plain text e-mail message, with JavaScript in a link reference element that is mishandled by linkref_addindex in rcube_string_replacer.php.

View vendor advisory

Published: 28 Dec 2020
Exploitation Reported: 22 Jun 2023
Attack vector: Remote
Complexity: Low
Privileges: None
User interaction: Required

CVE References

CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2020-35730
FEDORA-2021-2cb0643316 lists.fedoraproject.org · Vendor Advisory https://lists.fedoraproject.org/archives/list/package-announce%40list...
FEDORA-2021-73359af51c lists.fedoraproject.org · Vendor Advisory https://lists.fedoraproject.org/archives/list/package-announce%40list...
roundcube.net/download roundcube.net · CVE Record https://roundcube.net/download/
GitHub — roundcube/roundcubemail github.com · CVE Record https://github.com/roundcube/roundcubemail/compare/1.4.9...1.4.10
bugs.debian.org/cgi-bin/bugreport.cgi bugs.debian.org · CVE Record https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978491
alexbirnberg.com/roundcube-xss.html alexbirnberg.com · CVE Record https://www.alexbirnberg.com/roundcube-xss.html
GitHub — roundcube/roundcubemail github.com · CVE Record https://github.com/roundcube/roundcubemail/releases/tag/1.4.10
GitHub — roundcube/roundcubemail github.com · CVE Record https://github.com/roundcube/roundcubemail/releases/tag/1.3.16
GitHub — roundcube/roundcubemail github.com · CVE Record https://github.com/roundcube/roundcubemail/releases/tag/1.2.13

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 22 Jun 2023

Independent exploitation attestation added to the KEV Intelligence record.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

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Source	Added
CISA First	2023-06-22 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets: 0
User-Agents: 0

Raw values available in Pro and Enterprise.

Scanner coverage

Nessus template detected 02 Jun 2025.

View Nessus template

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner	Reference	Detected
Nessus	https://www.tenable.com/plugins/nessus/183111	02 Jun 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

6.1 Medium

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

32.7%

Weaknesses

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

All CVSS Scores

CVSS v3.1 6.1 Medium

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v2.0 4.3 Medium

AV:N/AC:M/Au:N/C:N/I:P/A:N

Timeline

From disclosure to observed exploitation

02 Jun 2025
Nessus plugin available

Scanner coverage available
22 Jun 2023
Added to CISA KEV

Listed in the CISA Known Exploited Vulnerabilities catalog
28 Dec 2020
CVE published

Vulnerability disclosed publicly
27 Dec 2020
CVE ID reserved

Identifier reserved by the CNA

Pro API

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Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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Evidence confidence and provenance
First-party sensor telemetry
PoC and scanner references
Affected versions and enrichment
Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2020-35730

Free JSON includes basic KEV fields

{
  "cve_id": "CVE-2020-35730",
  "confidence": "Confirmed",
  "cvss_score": 6.1,
  "cvss_estimated": false,
  "epss_score": 0.32688,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

Early warning alerts

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