CVE-2020-35730
XSS in Roundcube Webmail ≤ 1.2.13
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NSummary
CVE-2020-35730 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Roundcube Webmail. Its CVSS base score is 6.1 (Medium).
Operationally, ranked in the top 2% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and SI-15 (Information Output Filtering) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
An XSS vulnerability, tracked as CVE-2020-35730 and assigned CWE-79, affects Roundcube Webmail versions prior to 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10. The flaw occurs in the linkref_addindex function of rcube_string_replacer.php, which mishandles JavaScript content placed inside link reference elements of incoming plain-text email messages.
An unauthenticated remote attacker can exploit the issue by crafting and sending a plain-text email containing malicious JavaScript within a link reference. When a recipient views the message through the Roundcube web interface, the script executes in the user's browser context, enabling limited cross-origin actions such as reading sensitive data or performing actions on the user's behalf, consistent with the CVSS 6.1 vector (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).
The GitHub release tags and commit comparisons for versions 1.2.13, 1.3.16, and 1.4.10 document the patches that correct the improper handling in rcube_string_replacer.php; administrators should upgrade to one of these fixed releases.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2020-23386
Vulnerability Data
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.
- CWE(s)
- KEV Date Added
- 22 June 2023
Related Threats
Likely ATT&CK TechniquesAI
Techniques this vulnerability likely enables, inferred from its description, weakness type, and attributed-actor tradecraft. Confidence is per-technique.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
Directly requires validation and sanitization of untrusted input (plain-text email linkrefs) before processing in rcube_string_replacer.php, blocking the JavaScript injection that causes this XSS.
Requires filtering of information output to users, ensuring malicious script content in rendered email links is removed or escaped before display in the webmail interface.
Mandates timely remediation of known flaws such as the improper handling in rcube_string_replacer.php by applying the vendor patches released in 1.2.13/1.3.16/1.4.10.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly target introduction of XSS via coding standards/testing (mostly), yet the single broad outcome leaves many specific neutralization vectors unaddressed (partial).
Patching and EOL replacement can remediate known XSS instances in libraries or frameworks (partial) but do nothing to enforce input neutralization in application code (none).
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Secure-coding testing and automated code-analysis tools are applied to detect improper neutralization of script-related content during web-page generation.
Knowledge exchange on emerging attack techniques and patches reduces the likelihood that cross-site scripting flaws remain unaddressed in deployed applications.
Operational indicators of compromise for web-application attacks can be incorporated into WAF or input-filtering rules, lowering the likelihood that unsanitized data reaches the browser.
Requiring language-specific secure-coding standards and automated scanning during the SDLC catches missing output encoding or improper neutralization of untrusted data before the software reaches production.
Secure-coding standards, SAST scans and removal of insecure code samples together eliminate the failure to neutralize script content that produces cross-site scripting flaws.
Webpage malware scanning and block-listing of known malicious sites reduce the likelihood that reflected or stored script payloads reach a user’s browser.