CVE-2026-35544: CWE-669 Incorrect Resource Transfer Between Spheres in Roundcube Webmail
CVE-2026-35544 is a medium severity vulnerability in Roundcube Webmail versions before 1. 5. 14 and 1. 6. 14. It involves insufficient sanitization of CSS in HTML email messages, allowing a bypass of fixed-position mitigations through the use of the ! important CSS directive. This vulnerability does not impact confidentiality or availability but can lead to integrity issues. No official patch or remediation level has been confirmed yet, and no known exploits are reported in the wild.
AI Analysis
Technical Summary
This vulnerability in Roundcube Webmail arises from inadequate sanitization of Cascading Style Sheets (CSS) within HTML email content. Specifically, the sanitization fails to properly handle the !important CSS directive, which can be used to bypass fixed-position mitigation controls. The issue affects versions prior to 1.5.14 and 1.6.14. The CVSS 3.1 base score is 5.3, reflecting a network attack vector with low complexity, no privileges required, no user interaction, and an impact limited to integrity. There is no vendor advisory or patch information available, and the vulnerability is not related to cloud services.
Potential Impact
The vulnerability allows an attacker to bypass fixed-position CSS mitigations in HTML emails, potentially enabling manipulation of the email display or interface integrity. There is no impact on confidentiality or availability. No known exploits exist in the wild at this time.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should exercise caution when opening HTML emails from untrusted sources. Monitor Roundcube's official channels for updates regarding patches or mitigations.
CVE-2026-35544: CWE-669 Incorrect Resource Transfer Between Spheres in Roundcube Webmail
Description
CVE-2026-35544 is a medium severity vulnerability in Roundcube Webmail versions before 1. 5. 14 and 1. 6. 14. It involves insufficient sanitization of CSS in HTML email messages, allowing a bypass of fixed-position mitigations through the use of the ! important CSS directive. This vulnerability does not impact confidentiality or availability but can lead to integrity issues. No official patch or remediation level has been confirmed yet, and no known exploits are reported in the wild.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability in Roundcube Webmail arises from inadequate sanitization of Cascading Style Sheets (CSS) within HTML email content. Specifically, the sanitization fails to properly handle the !important CSS directive, which can be used to bypass fixed-position mitigation controls. The issue affects versions prior to 1.5.14 and 1.6.14. The CVSS 3.1 base score is 5.3, reflecting a network attack vector with low complexity, no privileges required, no user interaction, and an impact limited to integrity. There is no vendor advisory or patch information available, and the vulnerability is not related to cloud services.
Potential Impact
The vulnerability allows an attacker to bypass fixed-position CSS mitigations in HTML emails, potentially enabling manipulation of the email display or interface integrity. There is no impact on confidentiality or availability. No known exploits exist in the wild at this time.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should exercise caution when opening HTML emails from untrusted sources. Monitor Roundcube's official channels for updates regarding patches or mitigations.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mitre
- Date Reserved
- 2026-04-03T03:59:48.463Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69cf565a0a160ebd92cd3ea3
Added to database: 4/3/2026, 5:55:38 AM
Last enriched: 4/10/2026, 9:15:36 AM
Last updated: 5/20/2026, 12:53:27 PM
Views: 67
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