CVE-2020-35730: Roundcube Webmail Cross-Site Scripting (XSS) Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 22 Jun 2023, 906 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 32.9%
EPSS score, percentile 98.4 of all scored records
- How severe?
- 6.1 Medium
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
CISA deadline 13 Jul 2023. Apply updates per vendor instructions.
- Which versions are affected?
Not stated. The CVE record gives vendor and product as “n/a” and the version as “unspecified”.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: 13 July 2023.
Advisories and patches
Linked from CISA's catalog entry
- https://roundcube.net/news/2020/12/27/security-updates-1.4.10-1.3.16-and-1.2.13
- https://nvd.nist.gov/vuln/detail/CVE-2020-35730
Affected products and versions
The CVE record does not name affected products or versions: vendor and product are “n/a” and the version is “unspecified”.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Roundcube Webmail contains a cross-site scripting (XSS) vulnerability that allows an attacker to send a plain text e-mail message with Javascript in a link reference element that is mishandled by linkref_addinindex in rcube_string_replacer.php.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2020-35730 to its Known Exploited Vulnerabilities (KEV) catalog on 22 Jun 2023.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 13 Jul 2023.
- The CVE record was published on 28 Dec 2020, 906 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 6.1 (Medium), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 32.9% (percentile 98.4), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 28 Dec 2020 | CVE record published |
| 22 Jun 2023 | Added to CISA KEV |
| 13 Jul 2023 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
More exploited Roundcube vulnerabilities
- CVE-2025-49113: RoundCube Webmail Deserialization of Untrusted Data Vulnerability
- CVE-2025-68461: RoundCube Webmail Cross-site Scripting Vulnerability
- CVE-2024-42009: RoundCube Webmail Cross-Site Scripting Vulnerability
- CVE-2024-37383: RoundCube Webmail Cross-Site Scripting (XSS) Vulnerability
- CVE-2020-13965: Roundcube Webmail Cross-Site Scripting (XSS) Vulnerability
- CVE-2023-43770: Roundcube Webmail Persistent Cross-Site Scripting (XSS) Vulnerability