Remote content blocking bypass in Roundcube Webmail via CSS escapes
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
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
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
Timeline
- 2026-10-22 Threatist record created from CVE-2026-114728
- 2026-10-22 Alias added: GHSA-9x5r-8c78-gq2p
- 2026-10-26 CISA SSVC decision points changed
- 2026-10-29 Affected versions changed · Red Hat
- 2026-10-29 CVSS score added · Red Hat
References
Patch 4
- https://github.com/roundcube/roundcubemail/commit/2f74267f0e13bed7182b1d2294cc4f3c5c46dcee
- https://github.com/roundcube/roundcubemail/releases/tag/1.7.5
- https://github.com/roundcube/roundcubemail/releases/tag/1.6.20
- https://github.com/roundcube/roundcubemail/commit/ff4fcfdd2952f9d09947cc9c18137f381f27caf1
More Roundcube Webmail vulnerabilities
- 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
Sources
- CVE-2026-114728 · CVE Program
- CVE-2026-114728 · NVD
- FIRST EPSS
- GHSA-9x5r-8c78-gq2p · GitHub Advisory Database · CC BY 4.0
- CVE-2026-114728 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences