In Roundcube Webmail before 1.6.18 and 1.7.x before 1.7.3, 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. This issue exists because of insufficient fixes for CVE-2026-35540, CVE-2026-48843 and CVE-2026-62643.

The remote web server is running Roundcube Webmail version 1.6.x prior to 1.6.18 or 1.7.x prior to 1.7.3. It is, therefore, affected by multiple vulnerabilities:

  - The cmd_learn driver of the markasjunk plugin is subject to remote code execution via crafted placeholder     replacement values. This issue only affects Roundcube instances using the markasjunk plugin with its cmd_learn     driver. (CVE-2026-74997)

  - Mail search and LITERAL+ byte-count desynchronization could lead to information disclosure or privilege     escalation via IMAP command injection. (CVE-2026-75002)

  - Responses from the CSS (Cascading Style Sheets) proxy were not validated, which may result in information     disclosure or XSS (cross-site scripting) via MIME sniffing. (CVE-2026-74998)

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 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6479 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6479-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     August 30, 2026                       https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : roundcube     CVE ID         : CVE-2026-74997 CVE-2026-74998 CVE-2026-74999 CVE-2026-75000                      CVE-2026-75002 CVE-2026-75003 CVE-2026-75004 CVE-2026-75006                      CVE-2026-75007 CVE-2026-75010     Debian Bug     : 1144059

    Multiple vulnerabilities were discovered in roundcube, a skinnable AJAX     based webmail solution for IMAP servers, which could result in     cross-site scripting, SSRF bypass, information disclosure, privilege     escalation, denial of service or remote code execution.

    For the stable distribution (trixie), these problems have been fixed in     version 1.6.18+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 / 12 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4760 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4760-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                       Guilhem Moulin     August 29, 2026                               https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : roundcube     Version        : 1.4.15+dfsg.1-1+deb11u11 1.6.5+dfsg-1+deb12u11     CVE ID         : CVE-2026-74997 CVE-2026-74998 CVE-2026-74999 CVE-2026-75000                      CVE-2026-75002 CVE-2026-75003 CVE-2026-75004 CVE-2026-75006                      CVE-2026-75007 CVE-2026-75010     Debian Bug     : 1144059

    Multiple vulnerabilities were discovered in Roundcube, a skinnable AJAX based     webmail solution for IMAP servers, which could result in cross-site scripting,     server-side request forgery, information disclosure, privilege escalation, IMAP     injection, account takeover, or remote code execution.

    CVE-2026-74997

        A remote code execution vulnerability was found in the cmd_learn learning         driver of the markasjunk plugin.  Placeholders such as %u (username), %l         (localpart) and %d (domainpart) were injected with insufficiently         sanitized/escaped values used within a `sh -c ''` shell construction,         thereby allowing remote code execution from the user used to run roundcube         (by default www-data).

        Only installations where 1/ the markasjunk plugin was enabled, and 2/         where the `$config['markasjunk_learning_driver']` setting was set to         `cmd_learn`, were affected by this vulnerability.  In particular, stock         installations were not affected since the plugin is not enabled by default.

    CVE-2026-74998

        Content proxied by the CSS proxy (which is used to retrieve remote style         sheets linked to in text/html emails) was found to be lacking basic         validation, which may result in information disclosure or XSS (cross-site         scripting) via MIME sniffing.

    CVE-2026-74999

        Paulos Yibelo discovered that the Add to address book action was subject         to stored XSS due to insufficient sanitization of error messages and         information popups.

    CVE-2026-75000

        Insufficient HTML/CSS sanitization may lead to remote image blocking bypass         or XSS via crafted SVG animate `by` attribute sent in malicious text/html         emails.

    CVE-2026-75002

        Zach Hanley discovered that mail search and RFC2088 IMAP4 LITERAL+         byte-count desynchronization may lead to IMAP command injection.

    CVE-2026-75003

        Milan Hoppe discovered that insufficient HTML/CSS sanitization may lead to         remote image blocking bypass or XSS via unclosed url() in a FuncIRI         attribute.

    CVE-2026-75004

        Milan Hoppe discovered that managesieve rule names were not sanitized,         thereby allowing arbitrary sieve injection and bypass of the         managesieve_disabled_actions restriction set by an administrator.

        This vulnerability only affects installations where the managesieve plugin         is enabled.  In particular, stock installations were not affected since the         plugin is not enabled by default.

    CVE-2026-75006

        Dmytro Ivanenko and Milan Hoppe discovered that that the CSS sanitization         fixes for CVE-2026-35540, CVE-2026-48843 and CVE-2026-62643 were         insufficient, allowing a malicious embedded stylesheet in a text/html email         to lead to SSRF or information disclosure.

    CVE-2026-75007

        Milan Hoppe discovered that the LDAP integration was subject to filter         injection via unescaped %u/%fu/%d substitution.

    CVE-2026-75010

        The modoba driver of the password plugin was found to be leaking an         authentication token, which may lead to account takeover.

        Only installations where 1/ the password plugin was enabled, and 2/         where the `$config['password_driver']` setting was set to `modoboa`,         were affected by this vulnerability.  In particular, stock installations         were not affected since the password plugin is not enabled by default.

    For Debian 11 bullseye, these problems have been fixed in version     1.4.15+dfsg.1-1+deb11u11.

    For Debian 12 bookworm, these problems have been fixed in version     1.6.5+dfsg-1+deb12u11.

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

  - In Roundcube Webmail before 1.6.18 and 1.7.x before 1.7.3, 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. This issue exists because of insufficient fixes for CVE-2026-35540,     CVE-2026-48843 and CVE-2026-62643. (CVE-2026-75006)

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

ID	Name	Product	Family	Type	Severity
342614	Roundcube Webmail 1.6.x < 1.6.18 / 1.7.x < 1.7.3 Multiple Vulnerabilities	Nessus	CGI abuses	Remote	high
341608	Debian dsa-6479 : roundcube - security update	Nessus	Debian Local Security Checks	Local	high
341564	Debian dla-4760 : roundcube - security update	Nessus	Debian Local Security Checks	Local	critical
337113	Linux Distros Unpatched Vulnerability : CVE-2026-75006	Nessus	Misc.	Local	medium

Detections

Analytics

CVE-2026-75006

medium

Tenable Plugins

high

high

critical

medium