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Remote content blocking bypass in Roundcube Webmail via CSS escapes

Priority LOW 30CWE-184Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
Low · None · 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. The rcube_washtml sanitizer detects CSS url() tokens with a pattern that misses some escaped spellings of the token, so those values are not recognized as remote content. An unauthenticated remote attacker can send an HTML message that loads remote content without the user's consent. (CWE-184)

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

Roundcube Webmail before 1.6.20 and 1.7.x before 1.7.5 is affected by a remote content blocking bypass in the handling of FuncIRI attributes. rcube_washtml detected the CSS url() token with a pattern that enumerated only some of its escaped spellings, so values using other CSS escape sequences, for example \000075rl( or u\72 l(, were not recognized and remote content was loaded from an HTML message without the user's consent. Upstream fixed this in the commit “Fix remote content blocking bypass via CSS escapes in FuncIRI attributes (again)”, which resolves CSS escapes before matching and also inspects the `to`, `from` and `by` attributes.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00374 31st 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, which fix the flaw.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • 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-2026-114728
  2. 2026-10-22 Alias added: GHSA-9x5r-8c78-gq2p
  3. 2026-10-26 CISA SSVC decision points changed
  4. 2026-10-29 Affected versions changed · Red Hat
  5. 2026-10-29 CVSS score added · Red Hat

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