# CVE-2026-126813: Roundcube Webmail IMAP command injection in message cache

Source: https://junglewise.ai/threats/cve-2026-126813-roundcube-webmail-before-1-6-21-and-1-7-x-before-1-7-6-contains  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-11. Updated: 2026-11-11  
License: CC BY 4.0 with a link back

CVE-2026-126813 · Severity: medium · CVSS 6.8 · Published 2026-11-11

Roundcube Webmail is a web-based email client that connects to IMAP mail servers. An attacker can inject IMAP commands through specially crafted links that trick logged-in users into opening them, allowing the attacker to delete emails, change message flags, or modify mailbox permissions without the user's knowledge.

Technologies: [Roundcube Webmail](https://junglewise.ai/threats/technologies/webmail). Vendors: [Roundcube](https://junglewise.ai/threats/vendors/roundcube).

## Quick answers

**Is CVE-2026-126813 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-126813 being exploited in the wild.

**How severe is CVE-2026-126813?** Medium severity, with a CVSS score of 6.8, published 11 November 2026.

**Which products and versions are affected?** Roundcube Webmail before 1.6.21 and 1.7.x before 1.7.6.

**Is there a fix for CVE-2026-126813?** Yes: fixed in Roundcube Webmail 1.6.21, 1.7.6. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-126813 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-126813?** Check whether you run Roundcube Webmail at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Roundcube Webmail 1.6.21, 1.7.6

## Technical details

The vulnerability is an IMAP command injection flaw in the _uid parameter when messages_cache is enabled. A regex pattern failure allows CRLF characters to bypass validation in rcube_imap_generic.php, letting attackers inject arbitrary IMAP commands. The attack requires the victim to click a malicious GET link to the mail/show or mail/get endpoint while logged in.

## Affected products

- Roundcube Roundcube Webmail before 1.6.21 and 1.7.x before 1.7.6

## Timeline

- 2026-11-11: disclosed

## References

- [https://github.com/roundcube/roundcubemail/blob/1.7.5/program/lib/Roundcube/rcube_imap_generic.php](https://github.com/roundcube/roundcubemail/blob/1.7.5/program/lib/Roundcube/rcube_imap_generic.php)
- [https://github.com/roundcube/roundcubemail/commit/2ea63692178cab5cea486c7c630901b7f6852c80](https://github.com/roundcube/roundcubemail/commit/2ea63692178cab5cea486c7c630901b7f6852c80)

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