CVE-2020-35730

Exp

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.

Published: 2020-12-28 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-35730 is rated Active Exploitation (78.7/100): CVSS Medium severity, with high exploitation likelihood (EPSS 32.37%, 98th percentile). CISA KEV confirms active exploitation (added 2023-06-22) affecting Roundcube / Roundcube Webmail. cross-site scripting (CWE-79) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2020-35730

Name: Roundcube Webmail Cross-Site Scripting (XSS) Vulnerability · CISA KEV detail

Exploit added: 2023-06-22

Action due: 2023-07-13

Required action: Apply updates per vendor instructions.

Exploit prediction scoring system (EPSS) score for CVE-2020-35730

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 67.42% 32.37% -35.06%
2 2026-05-14 64.81% 67.42% +2.61%
3 2026-02-10 — 64.81% —

Full EPSS history (55 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-35730

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 134c704f-9b21-4f2e-91b3-4a467353bcc0
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2020-35730

OS Trackers for CVE-2020-35730

vendor priority summary link
debian not yet assigned CVE-2020-35730 not yet assigned priority: Debian including 1 source packages (roundcube), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-35730
ubuntu high CVE-2020-35730 high priority: Ubuntu including 1 source packages (roundcube), 15 status rows across 15 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): not-affected 9, released 4, DNE 1, ignored 1. https://ubuntu.com/security/CVE-2020-35730

Affected software / configurations for CVE-2020-35730

Vendor Product Version Raw CPE
roundcube webmail < 1.2.13 cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*
roundcube webmail >= 1.3.0, < 1.3.16 cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*
roundcube webmail >= 1.4, < 1.4.10 cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

References for CVE-2020-35730

URL Tags
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978491 Issue Tracking Mailing List
https://github.com/roundcube/roundcubemail/compare/1.4.9...1.4.10 Patch
https://github.com/roundcube/roundcubemail/releases/tag/1.2.13 Release Notes
https://github.com/roundcube/roundcubemail/releases/tag/1.3.16 Release Notes
https://github.com/roundcube/roundcubemail/releases/tag/1.4.10 Release Notes
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HCEU4BM5WGIDJWP6Z4PCH62ZMH57QYM2/ Mailing List Release Notes
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HMLIZWKMTRCLU7KZLEQHELS4INXJ7X5Q/ Mailing List Release Notes
https://roundcube.net/download/ Product
https://www.alexbirnberg.com/roundcube-xss.html Broken Link
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-35730 US Government Resource
cvelogic Threat Intelligence