Roundcube Webmail up to 1.6.13 HTML Mail Message resource transfer

CVSS Meta Temp Score
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CTI Interest Score
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5.4$0-$5k0.00

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.

The vulnerability scanner Nessus provides a plugin with the ID 304879 (Linux Distros Unpatched Vulnerability : CVE-2026-35540), which helps to determine the existence of the flaw in a target environment.

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.

The vulnerability is also documented in the databases at Tenable (304879) and CERT Bund (WID-SEC-2026-0789). Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Open Source Roundcube

Productinfo

Type

Vendor

Name

Version

License

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

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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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

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 304879
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-35540

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
04/07/2026 +4 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
CERT Bund: WID-SEC-2026-0789 - Roundcube: Mehrere Schwachstellen

Entryinfo

Created: 04/03/2026 07:48
Updated: 04/07/2026 08:04
Changes: 04/03/2026 07:48 (67), 04/05/2026 14:19 (2), 04/07/2026 08:04 (7)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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