CVE-2026-35540 | Roundcube Webmail up to 1.6.13 HTML Mail Message resource transfer

VDB-355063 · CVE-2026-35540 · GCVE-0-2026-35540 ROUNDCUBE WEBMAIL UP TO 1.6.13 HTML MAIL MESSAGE RESOURCE TRANSFER HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 5.4 $0-$5k 1.68 Summaryinfo A vulnerability identified as problematic has been detected in Roundcube Webmail up to 1.6.13. Impacted is an unknown function of the component HTML Mail Message Handler. This manipulation causes resource transfer. This vulnerability appears as CVE-2026-35540. The attack may be initiated remotely. There is no available exploit. You should upgrade the affected component. Detailsinfo A vulnerability has been found in Roundcube Webmail up to 1.6.13 and classified as problematic. Affected by this vulnerability is some unknown functionality of the component HTML Mail Message Handler. The manipulation with an unknown input leads to a resource transfer vulnerability. The CWE definition for the vulnerability is CWE-669. The product does not properly transfer a resource/behavior to another sphere, or improperly imports a resource/behavior from another sphere, in a manner that provides unintended control over that resource. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is: An issue was discovered in Roundcube Webmail 1.6.0 before 1.6.14. Insufficient Cascading Style Sheets (CSS) sanitization in HTML e-mail messages may lead to SSRF or Information Disclosure, e.g., if stylesheet links point to local network hosts. It is possible to read the advisory at roundcube.net. This vulnerability is known as CVE-2026-35540 since 04/03/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. Upgrading to version 1.6.14 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 27ec6cc9cb25e1ef8b4d4ef39ce76d619caa6870 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version. Productinfo Type Mail Client Software Vendor Roundcube Name Webmail Version 1.6.0 1.6.1 1.6.2 1.6.3 1.6.4 1.6.5 1.6.6 1.6.7 1.6.8 1.6.9 1.6.10 1.6.11 1.6.12 1.6.13 License free CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 5.5 VulDB Meta Temp Score: 5.4 VulDB Base Score: 5.6 VulDB Temp Score: 5.4 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 5.4 CNA Vector (MITRE): 🔒 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Resource transfer CWE: CWE-669 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: Webmail 1.6.14 Patch: 27ec6cc9cb25e1ef8b4d4ef39ce76d619caa6870 Timelineinfo 04/03/2026 Advisory disclosed 04/03/2026 +0 days CVE reserved 04/03/2026 +0 days VulDB entry created 04/03/2026 +0 days VulDB entry last update Sourcesinfo Advisory: roundcube.net Status: Confirmed CVE: CVE-2026-35540 (🔒) GCVE (CVE): GCVE-0-2026-35540 GCVE (VulDB): GCVE-100-355063 Entryinfo Created: 04/03/2026 07:48 Changes: 04/03/2026 07:48 (67) Complete: 🔍 Cache ID: 99:FC3:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸