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CSS scoping bypass in Roundcube Webmail HTML messages

Priority LOW 34CWE-669Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
Low · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

Roundcube Webmail from 1.6.0 before 1.6.20 and from 1.7.0 before 1.7.5 is affected. Its CSS scoping for HTML messages fails for selectors that follow an at-rule such as @layer, so styles reach the whole interface instead of only the message body (CWE-669). A remote attacker without privileges can send an HTML message that restyles the interface, enabling UI redressing and spoofing.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

Roundcube Webmail before 1.6.20 and 1.7.x before 1.7.5 is affected by a CSS scoping bypass in HTML messages. rcube_utils::mod_css_styles() did not treat an at-rule prologue such as @layer a; as a selector boundary, and did not handle selectors beginning with ::, so selectors following an at-rule were left unscoped and applied to the whole Roundcube interface instead of being confined to the message body. This allows an HTML message to restyle application chrome for UI redressing and spoofing. Upstream fixed this in the commit “Fix CSS scoping bypass in HTML messages using at-rules”.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00252 16th percentileScored 2026-11-07
Fix Fixed Webmail (Roundcube): 1.6.20, 1.7.5

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
RoundcubeWebmail1.6.0 to before 1.6.20; 1.7.0 to before 1.7.51.6.20, 1.7.5Patch availableCNA
  • Webmail VendorRoundcube Affected 1.6.0 to before 1.6.20; 1.7.0 to before 1.7.5 Fixed in 1.6.20, 1.7.5 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*1.6.0 to before 1.6.20; 1.7.0 to before 1.7.5VulnerableRoundcube
  • cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:* Versions 1.6.0 to before 1.6.20; 1.7.0 to before 1.7.5 Vulnerable ·Roundcube

Remediation

Upgrade Roundcube Webmail to version 1.6.20 or 1.7.5, whichever is the fixed release for the installed version.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA Webmail (Roundcube) Fixed in 1.6.20, 1.7.5

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Advisory ·

    Roundcube Webmail — roundcube.net/news/2026/10/19/security-updates-1.6.20-and-1…

    20 records Highest priority Priority LOW 20 LOW

    Other records, highest priority first

    • TI-2026-79180 Server-side request forgery filter bypass in Roundcube WebmailPriority LOW 38
    • TI-2026-79177 Roundcube Webmail passes unsafe SVG and EPS content to ImageMagickPriority LOW 38
    • TI-2026-79182 Improper authentication in Roundcube Webmail multi-host alias loginsPriority LOW 37

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-22 Threatist record created from CVE-2026-114722
  2. 2026-10-22 Alias added: GHSA-jg35-cc9w-63m9
  3. 2026-10-23 Affected versions changed · Red Hat
  4. 2026-10-23 CVSS score added · Red Hat
  5. 2026-10-23 Priority changed: MEDIUM → LOW
  6. 2026-10-28 CISA SSVC decision points changed

References

  • TI-2025-31204 Deserialization of untrusted data in Roundcube Webmail KEVCVSS 3.1CRITICAL 9.9
  • TI-2021-19778 Roundcube before 1.3.17 and 1.4.x before 1.4.12 is prone to a potential SQL injection via search or search_params. KEVCVSS 3.1CRITICAL 9.8
  • TI-2020-10051 rcube_image.php in Roundcube Webmail before 1.4.4 allows attackers to execute arbitrary… KEVCVSS 3.1CRITICAL 9.8
  • TI-2024-28025 A Cross-Site Scripting vulnerability in Roundcube through 1.5.7 and 1.6.x through 1.6.7… KEVCVSS 3.1CRITICAL 9.3
  • TI-2017-12250 Roundcube Webmail before 1.1.10, 1.2.x before 1.2.7, and 1.3.x before 1.3.3 allows… KEVCVSS 3.1HIGH 7.8
  • TI-2025-41994 Cross-site scripting in Roundcube Webmail KEVCVSS 3.1HIGH 7.2
See all 112 →

Sources