CVE-2026-35540

Roundcube Webmail: Insufficient CSS sanitization in HTML e-mail messages

5.4 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.40%Up 0.4 points since Apr 3, 2026

What each source reports

CVE List Score used 5.4

Record: CVE-2026-35540
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness: CWE-669
Updated: 2026-11-02

EUVDEUVD-2026-18583 5.4

Record: EUVD-2026-18583
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-vxg2-hhgr-37fx 5.4

Roundcube Webmail: Insufficient CSS sanitization in HTML e-mail messages

Record: GHSA-vxg2-hhgr-37fx
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness: CWE-669, CWE-918
Updated: 2026-11-02

NVD 5.4

Record: CVE-2026-35540
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness: CWE-669
Updated: 2026-11-02

OSV 5.4

Record: CVE-2026-35540
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness: CWE-669
Updated: 2026-11-02

OSVDEBIAN-CVE-2026-35540 6.5

Record: DEBIAN-CVE-2026-35540
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Updated: 2026-11-02

OSVGHSA-vxg2-hhgr-37fx 5.4

Roundcube Webmail: Insufficient CSS sanitization in HTML e-mail messages

Record: GHSA-vxg2-hhgr-37fx
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness: CWE-669, CWE-918
Updated: 2026-11-02

OSVUBUNTU-CVE-2026-35540 5.4

Record: UBUNTU-CVE-2026-35540
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`roundcube/roundcubemail` Packagist	1.7-beta up to 1.7-rc5	1.7-rc5
`roundcube` Debian:12	before 1.6.5+dfsg-1+deb12u8, plus listed versions 1.6.1+dfsg-11.6.2+dfsg-11.6.3+dfsg-11.6.3+dfsg-1~deb12u11.6.3+dfsg-2 Show 10 moreShow less 1.6.4+dfsg-11.6.4+dfsg-1~deb12u11.6.5+dfsg-11.6.5+dfsg-1+deb12u21.6.5+dfsg-1+deb12u31.6.5+dfsg-1+deb12u41.6.5+dfsg-1+deb12u51.6.5+dfsg-1+deb12u61.6.5+dfsg-1+deb12u71.6.5+dfsg-1~deb12u1	1.6.5+dfsg-1+deb12u8
`roundcube` Debian:13	before 1.6.15+dfsg-0+deb13u1, plus listed versions 1.6.11+dfsg-11.6.12+dfsg-0+deb13u11.6.12+dfsg-11.6.13+dfsg-0+deb13u11.6.13+dfsg-11.6.14+dfsg-1	1.6.15+dfsg-0+deb13u1
`roundcube` Debian:14	before 1.6.14+dfsg-1, plus listed versions 1.6.11+dfsg-11.6.12+dfsg-11.6.13+dfsg-1	1.6.14+dfsg-1
`roundcube/roundcubemail` Packagist	1.7-beta up to 1.7-rc5, plus listed versions 1.7-beta21.7-rc1.7-rc21.7-rc31.7-rc4	1.7-rc5
`roundcube` Ubuntu:Pro:16.04:LTS	All versions, plus listed versions 1.1.1+dfsg.1-21.1.2+dfsg.1-51.1.3+dfsg.1-11.1.4+dfsg.1-11.2~beta+dfsg.1-0ubuntu1 Show 8 moreShow less 1.2~beta+dfsg.1-0ubuntu1+esm11.2~beta+dfsg.1-0ubuntu1+esm21.2~beta+dfsg.1-0ubuntu1+esm31.2~beta+dfsg.1-0ubuntu1+esm41.2~beta+dfsg.1-0ubuntu1+esm51.2~beta+dfsg.1-0ubuntu1+esm61.2~beta+dfsg.1-0ubuntu1+esm71.2~beta+dfsg.1-0ubuntu1+esm8	None known
`roundcube` Ubuntu:Pro:18.04:LTS	All versions, plus listed versions 1.3.0+dfsg.1-11.3.1+dfsg.1-11.3.3+dfsg.1-11.3.3+dfsg.1-21.3.6+dfsg.1-1 Show 8 moreShow less 1.3.6+dfsg.1-1ubuntu0.1~esm11.3.6+dfsg.1-1ubuntu0.1~esm21.3.6+dfsg.1-1ubuntu0.1~esm31.3.6+dfsg.1-1ubuntu0.1~esm41.3.6+dfsg.1-1ubuntu0.1~esm51.3.6+dfsg.1-1ubuntu0.1~esm61.3.6+dfsg.1-1ubuntu0.1~esm71.3.6+dfsg.1-1ubuntu0.1~esm8	None known
`roundcube` Ubuntu:Pro:20.04:LTS	All versions, plus listed versions 1.3.8+dfsg.1-21.3.10+dfsg.1-11.4.1+dfsg.1-21.4.2+dfsg.1-11.4.2+dfsg.1-2 Show 9 moreShow less 1.4.3+dfsg.1-11.4.3+dfsg.1-1ubuntu0.1~esm11.4.3+dfsg.1-1ubuntu0.1~esm21.4.3+dfsg.1-1ubuntu0.1~esm31.4.3+dfsg.1-1ubuntu0.1~esm41.4.3+dfsg.1-1ubuntu0.1~esm51.4.3+dfsg.1-1ubuntu0.1~esm61.4.3+dfsg.1-1ubuntu0.1~esm71.4.3+dfsg.1-1ubuntu0.1~esm8	None known
`roundcube` Ubuntu:Pro:22.04:LTS	All versions, plus listed versions 1.4.11+dfsg.1-41.5.0+dfsg.1-21.5.0+dfsg.1-2ubuntu0.1~esm11.5.0+dfsg.1-2ubuntu0.1~esm21.5.0+dfsg.1-2ubuntu0.1~esm31.5.0+dfsg.1-2ubuntu0.1~esm41.5.0+dfsg.1-2ubuntu0.1~esm51.5.0+dfsg.1-2ubuntu0.1~esm6	None known
`roundcube` Ubuntu:Pro:24.04:LTS	All versions, plus listed versions 1.6.2+dfsg-11.6.4+dfsg-11.6.5+dfsg-11.6.6+dfsg-11.6.6+dfsg-2 Show 4 moreShow less 1.6.6+dfsg-2ubuntu0.11.6.6+dfsg-2ubuntu0.1+esm11.6.6+dfsg-2ubuntu0.1+esm21.6.6+dfsg-2ubuntu0.1+esm3	None known
`roundcube` Ubuntu:25.10	All versions, plus listed versions 1.6.10+dfsg-11.6.10+dfsg-21.6.11+dfsg-1	None known
`roundcube` Ubuntu:26.10	All versions, plus listed versions 1.6.11+dfsg-1	None known
`roundcube` Ubuntu:Pro:26.04:LTS	All versions, plus listed versions 1.6.11+dfsg-11.6.11+dfsg-1ubuntu0.26.04.1~esm1	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-35540 is a medium vulnerability (CVSS 5.4) in Bulwarkmail Webmail, published April 3, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.40%, the 34th percentile. Fixed in roundcube/roundcubemail 1.7-rc5.

References

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