CVE-2026-35543: Roundcube Webmail remote image blocking bypass in SVG content

CVE-2026-35543 · Severity: medium · CVSS 5.3 · Published 2026-04-03

Roundcube Webmail, a widely used open-source email client, contains a security flaw in how it handles images in emails. An attacker can send a specially crafted email that bypasses the software's privacy protections, which are designed to block remote images from loading automatically. This could allow an attacker to track when a user opens an email or potentially bypass certain access controls, compromising user privacy.

Technologies: roundcube/roundcubemail (Packagist), Roundcube Webmail. Vendors: Packagist, Roundcube.

Quick answers

Is CVE-2026-35543 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-35543 being exploited in the wild.
How severe is CVE-2026-35543?
Medium severity, with a CVSS score of 5.3, published 3 April 2026.
Which products and versions are affected?
roundcube/roundcubemail (Packagist) ECOSYSTEM:introduced=1.7-beta,fixed=1.7-rc5; Roundcube Webmail < 1.5.14, 1.6.x < 1.6.14.
Is there a fix for CVE-2026-35543?
Yes. roundcube/roundcubemail (Packagist): upgrade to 1.7-rc5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-35543 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-35543?
Check whether you run roundcube/roundcubemail (Packagist) or 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

  • roundcube/roundcubemail (Packagist): upgrade to 1.7-rc5 or later
    composer require roundcube/roundcubemail:^1.7-rc5

Technical details

A vulnerability in Roundcube Webmail's HTML sanitization component (rcube_washtml.php) allows attackers to bypass remote image blocking. By using SVG content containing specific 'animate' attributes within an email message, an attacker can force the webmail client to load external resources even when the user has configured the application to block remote content. This is classified as an Incorrect Resource Transfer Between Spheres (CWE-669). The issue is triggered automatically upon viewing the email without requiring further user interaction. Patches have been released in versions 1.5.14, 1.6.14, and 1.7-rc5.

Affected products

  • Roundcube Webmail < 1.5.14, 1.6.x < 1.6.14

Identifiers

  • CVE-2026-35543
  • GHSA-j2g6-8rvg-7mf6

Timeline

  • 2026-03-18: patched: Security updates 1.5.14 and 1.6.14 released.
  • 2026-04-03: disclosed: Initial CVE publication.

References

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