Roundcube Webmail before 1.5.13 and 1.6 before 1.6.13, when "Block remote images" is used, does not block SVG feImage.

The remote Debian 12 / 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6137 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6137-1                   security@debian.org     https://www.debian.org/security/                       Sebastien Delafond     February 17, 2026                     https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : roundcube     CVE ID         : CVE-2026-25916 CVE-2026-26079     Debian Bug     : 1127447

    CERT Polska and nullcathedral discovered that roundcube, a skinnable     AJAX based webmail solution for IMAP servers, did not correctly     process and sanitize requests. This would allow an attacker to perform     CSS injection attacks, or leak sensitive information.

    For the oldstable distribution (bookworm), these problems have been fixed     in version 1.6.5+dfsg-1+deb12u7.

    For the stable distribution (trixie), these problems have been fixed in     version 1.6.13+dfsg-0+deb13u1.

    We recommend that you upgrade your roundcube packages.

    For the detailed security status of roundcube please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/roundcube

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 11 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4480 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4480-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                       Guilhem Moulin     February 17, 2026                             https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : roundcube     Version        : 1.4.15+dfsg.1-1+deb11u7     CVE ID         : CVE-2026-25916 CVE-2026-26079     Debian Bug     : 1127447

    Vulnerabilities were discovered in Roundcube, a skinnable AJAX based     webmail solution for IMAP servers, which might lead to information     disclosure or privilege escalation.

    CVE-2026-25916

        NULL CATHEDRAL discovered that the HTML sanitizer doesn't treat SVG         `<feImage href=>` as an image source.  This allows attackers to         bypass remote image blocking to track email open action or         potentially bypass access control.

    CVE-2026-26079

        CERT Polska discovered that CSS code in text/html emails were         insufficiently sanitized, allowing an attacker to inject malicious         stylesheet rules.

    For Debian 11 bullseye, these problems have been fixed in version     1.4.15+dfsg.1-1+deb11u7.

    We recommend that you upgrade your roundcube packages.

    For the detailed security status of roundcube please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/roundcube

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS     Attachment:
    signature.asc     Description: PGP signature

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote web server is running Roundcube Webmail version 1.5.x prior to 1.5.13 or 1.6.x prior to 1.6.13. It is, therefore, affected by multiple vulnerabilities:

  - A Cascading Style Sheets (CSS) injection vulnerability exists due to mishandling of comments. A remote attacker     could exploit this to inject arbitrary CSS. (CVE-2026-26079)

  - A remote image blocking bypass exists because SVG feImage elements are not blocked when the 'Block remote images'     setting is used. A remote attacker could exploit this to load remote images. (CVE-2026-25916)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - Roundcube Webmail before 1.5.13 and 1.6 before 1.6.13, when Block remote images is used, does not block     SVG feImage. (CVE-2026-25916)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
299290	Debian dsa-6137 : roundcube - security update	Nessus	Debian Local Security Checks	medium
299289	Debian dla-4480 : roundcube - security update	Nessus	Debian Local Security Checks	medium
298770	Roundcube Webmail 1.5.x < 1.5.13 / 1.6.x < 1.6.13 Multiple Vulnerabilities	Nessus	CGI abuses	medium
298453	Linux Distros Unpatched Vulnerability : CVE-2026-25916	Nessus	Misc.	medium

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