In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel, which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will become mounted inside the sandbox.

Security Update for Flatpak

The AlmaLinux 9.2 host has packages installed that are affected by a vulnerability as referenced in the TuxCare ALMALINUX9.2:CLSA-2026:1789979782 advisory.

  - In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on     the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than     CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and     /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-     controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-     mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains     attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel,     which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will     become mounted inside the sandbox. (CVE-2026-90616)

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

The AlmaLinux 9.6 host has packages installed that are affected by a vulnerability as referenced in the TuxCare ALMALINUX9.6:CLSA-2026:1790035964 advisory.

  - In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on     the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than     CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and     /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-     controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-     mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains     attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel,     which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will     become mounted inside the sandbox. (CVE-2026-90616)

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

The Rocky Linux 9.6 host has packages installed that are affected by a vulnerability as referenced in the TuxCare ALMALINUX9.6:CLSA-2026:1790035964 advisory.

  - In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on     the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than     CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and     /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-     controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-     mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains     attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel,     which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will     become mounted inside the sandbox. (CVE-2026-90616)

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

The CentOS Linux 7 host has packages installed that are affected by a vulnerability as referenced in the TuxCare CENTOS7:CLSA-2026:1789577977 advisory.

  - In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on     the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than     CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and     /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-     controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-     mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains     attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel,     which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will     become mounted inside the sandbox. (CVE-2026-90616)

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

The version of flatpak installed on the remote host is prior to 1.0.9-10. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3959 advisory.

    In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on     the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than     CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and     /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-     controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-     mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains     attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel,     which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will     become mounted inside the sandbox. (CVE-2026-90616)

    A malicious or compromised Flatpak repository can write attacker-controlled content to arbitrary locations     on the host filesystem via extract_extra_data(). On system installs, the write happens as root. Two issues     combine: `files/extra` is resolved via path operations that follow symlinks, and blob names from     `xa.extra-data-sources` are not sanitized against `..` traversal. (CVE-2026-96275)

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

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

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3143 advisory.

    A flaw was found in Flatpak. A Time-of-check to time-of-use (TOCTOU) race condition exists in the     `org.freedesktop.Flatpak.SystemHelper` component. This vulnerability occurs because a privileged `chmod`     operation executes before the OSTree repository validation within the `Deploy()` function. An attacker can     exploit this timing window to redirect symlinks to arbitrary files, potentially leading to unauthorized     file manipulation or information disclosure. (CVE-2026-76925)

    In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on     the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than     CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and     /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-     controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-     mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains     attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel,     which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will     become mounted inside the sandbox. (CVE-2026-90616)

    A malicious or compromised Flatpak repository can write attacker-controlled content to arbitrary locations     on the host filesystem via extract_extra_data(). On system installs, the write happens as root. Two issues     combine: `files/extra` is resolved via path operations that follow symlinks, and blob names from     `xa.extra-data-sources` are not sanitized against `..` traversal. (CVE-2026-96275)

    In Flatpak before 1.18.1, the revokefs writer, used by the flatpak-system-helper to receive repository     data from unprivileged callers, validated file paths by rejecting literal .. components but did not     prevent symlink traversal. A malicious local user in an active local session could obtain two revokefs     sessions via the system helper, create a symlink in one session pointing into the other session's     directory, and retain a file descriptor through that symlink. This allowed the attacker to modify files     belonging to a different revokefs session after they had been validated and imported by the system helper.
    In particular, an attacker could use this to tamper with ostree commit objects in the system repository     after they passed signature verification, enabling root-controlled file writes to attacker-chosen paths     and local root privilege escalation. (CVE-2026-96808)

Tenable has extracted the preceding description block directly from the tested product 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 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6524 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6524-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     September 28, 2026                    https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : flatpak     CVE ID         : CVE-2026-90616 CVE-2026-92162 CVE-2026-97023 CVE-2026-97024                      CVE-2026-97025 CVE-2026-97026 CVE-2026-97027 CVE-2026-97029

    Multiple security vulnerabilities were discovered in Flatpak, an     application deployment framework for desktop apps, which could result in     denial service via malicious applications or information disclosure.

    For the stable distribution (trixie), these problems have been fixed in     version 1.16.6-1~deb13u3.

    We recommend that you upgrade your flatpak packages.

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

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

  - In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on     the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than     CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and     /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker-     controlled. Missing symlink protection can redirect the directories. Some of these directories are bind-     mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains     attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel,     which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will     become mounted inside the sandbox. (CVE-2026-90616)

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

ID	Name	Product	Family	Type	Severity
361747	AlmaLinux 9.2 [TuxCare] Security Update: flatpak / flatpak-devel / flatpak-libs / flatpak-selinux / etc (ALMALINUX9.2:CLSA-2026:1789979782)	Nessus	Alma Linux Local Security Checks	Local	high
360535	AlmaLinux 9.6 [TuxCare] Security Update: flatpak / flatpak-devel / flatpak-libs / flatpak-selinux / etc (ALMALINUX9.6:CLSA-2026:1790035964)	Nessus	Alma Linux Local Security Checks	Local	high
360514	Rocky Linux 9.6 [TuxCare] Security Update: flatpak / flatpak-devel / flatpak-libs / flatpak-selinux / etc (ALMALINUX9.6:CLSA-2026:1790035964)	Nessus	Rocky Linux Local Security Checks	Local	high
352961	CentOS Linux 7 [TuxCare] Security Update: flatpak / flatpak-builder / flatpak-devel / flatpak-libs (CENTOS7:CLSA-2026:1789577977)	Nessus	CentOS Local Security Checks	Local	high
351069	Amazon Linux 2 : flatpak (ALAS-2026-3959)	Nessus	Amazon Linux Local Security Checks	Local	high
351027	Amazon Linux 2023 : flatpak, flatpak-devel, flatpak-libs (ALAS2023-2026-3143)	Nessus	Amazon Linux Local Security Checks	Local	high
350953	Debian dsa-6524 : flatpak - security update	Nessus	Debian Local Security Checks	Local	high
345465	Linux Distros Unpatched Vulnerability : CVE-2026-90616	Nessus	Misc.	Local	high

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