# CVE-2021-41133: Sandbox bypass via recent VFS-manipulating syscalls > Flatpak apps can bypass sandbox restrictions by manipulating the virtual filesystem to trick host services into granting elevated privileges. - **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 8 Oct 2021 - **Updated:** 4 Aug 2024 - **Also known as:** ALEA-2021:4539, ALSA-2021:4042, CLEANSTART-2024-JX19003, DEBIAN-CVE-2021-41133, DSA-4984-1, GHSA-67h7-w3jq-vh4q, MGASA-2021-0486, OESA-2021-1404, RHSA-2021:4042, RHSA-2021:4044, RHSA-2021:4106, RHSA-2021:4107, RLSA-2021:4042, SUSE-SU-2021:3472-1, SUSE-SU-2022:3439-1, UBUNTU-CVE-2021-41133, USN-5191-1, openSUSE-SU-2021:1400-1, openSUSE-SU-2021:3472-1, openSUSE-SU-2024:11574-1 ## What is CVE-2021-41133? CVE-2021-41133 is a high-severity vulnerability in Debian Debian Linux, published on 8 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In versions prior to 1.10.4 and 1.12.0, Flatpak apps with direct access to AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can trick portals and other host-OS services into treating the Flatpak app as though it was an ordinary, non-sandboxed host-OS process. They can do this by manipulating the VFS using recent mount-related syscalls that are not blocked by Flatpak's denylist seccomp filter, in order to substitute a crafted `/.flatpak-info` or make that file disappear entirely. Flatpak apps that act as clients for AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can escalate the privileges that the corresponding services will believe the Flatpak app has. Note that protocols that operate entirely over the D-Bus session bus (user bus), system bus or accessibility bus are not affected by this. This is due to the use of a proxy process `xdg-dbus-proxy`, whose VFS cannot be manipulated by the Flatpak app, when interacting with these buses. Patches exist for versions 1.10.4 and 1.12.0, and as of time of publication, a patch for version 1.8.2 is being planned. There are no workarounds aside from upgrading to a patched version. Weakness: CWE-20 (Improper Input Validation) ## Which versions are affected by CVE-2021-41133? It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `flatpak` | AlmaLinux:8 | All versions | 1.8.5-4.el8_4 | | `flatpak` | AlmaLinux:8 | All versions | 1.8.5-5.el8_5 | | `flatpak-devel` | AlmaLinux:8 | All versions | 1.8.5-5.el8_5 | | `flatpak-libs` | AlmaLinux:8 | All versions | 1.8.5-4.el8_4 | | `flatpak-libs` | AlmaLinux:8 | All versions | 1.8.5-5.el8_5 | | `flatpak-selinux` | AlmaLinux:8 | All versions | 1.8.5-4.el8_4 | | `flatpak-selinux` | AlmaLinux:8 | All versions | 1.8.5-5.el8_5 | | `flatpak-session-helper` | AlmaLinux:8 | All versions | 1.8.5-4.el8_4 | | `flatpak-session-helper` | AlmaLinux:8 | All versions | 1.8.5-5.el8_5 | | `flatpak` | Red Hat:enterprise_linux:7::client | All versions | 0:1.0.9-12.el7_9 | | `flatpak-builder` | Red Hat:enterprise_linux:7::client | All versions | 0:1.0.0-12.el7_9 | | `flatpak-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:1.0.9-12.el7_9 | | `flatpak-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:1.0.9-12.el7_9 | | `flatpak-libs` | Red Hat:enterprise_linux:7::client | All versions | 0:1.0.9-12.el7_9 | | `flatpak` | Red Hat:enterprise_linux:7::computenode | All versions | 0:1.0.9-12.el7_9 | | `flatpak-builder` | Red Hat:enterprise_linux:7::computenode | All versions | 0:1.0.0-12.el7_9 | | `flatpak-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:1.0.9-12.el7_9 | | `flatpak-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:1.0.9-12.el7_9 | | `flatpak-libs` | Red Hat:enterprise_linux:7::computenode | All versions | 0:1.0.9-12.el7_9 | | `flatpak` | Red Hat:enterprise_linux:7::server | All versions | 0:1.0.9-12.el7_9 | | `flatpak-builder` | Red Hat:enterprise_linux:7::server | All versions | 0:1.0.0-12.el7_9 | | `flatpak-debuginfo` | Red Hat:enterprise_linux:7::server | All versions | 0:1.0.9-12.el7_9 | | `flatpak-devel` | Red Hat:enterprise_linux:7::server | All versions | 0:1.0.9-12.el7_9 | | `flatpak-libs` | Red Hat:enterprise_linux:7::server | All versions | 0:1.0.9-12.el7_9 | | `flatpak` | Red Hat:enterprise_linux:7::workstation | All versions | 0:1.0.9-12.el7_9 | | `flatpak-builder` | Red Hat:enterprise_linux:7::workstation | All versions | 0:1.0.0-12.el7_9 | | `flatpak-debuginfo` | Red Hat:enterprise_linux:7::workstation | All versions | 0:1.0.9-12.el7_9 | | `flatpak-devel` | Red Hat:enterprise_linux:7::workstation | All versions | 0:1.0.9-12.el7_9 | | `flatpak-libs` | Red Hat:enterprise_linux:7::workstation | All versions | 0:1.0.9-12.el7_9 | | `flatpak` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-libs` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-libs-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-selinux` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-session-helper` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-session-helper-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak-tests-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:1.8.5-4.el8_4 | | `flatpak` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:1.0.9-5.el8_1 | | `flatpak-debuginfo` | Red Hat:rhel_eus:8.1::appstream | All versions | 0:1.0.9-5.el8_1 | Products: Debian Debian Linux, Fedoraproject Fedora, Flatpak Flatpak. ## How do I fix CVE-2021-41133? Upgrade to a fixed version. ## Is CVE-2021-41133 being exploited? There is no known exploitation of CVE-2021-41133 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-41133 and fix it if it is affected. What it is: CVE-2021-41133 is a high-severity vulnerability in Debian Debian Linux, published on 8 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-41133 in the wild and no public exploit code. Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-41133/ (Markdown: https://insights.sbomify.com/CVE-2021-41133/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41133 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41133 - OSV: https://osv.dev/vulnerability/CVE-2021-41133 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-41133/ Summaries are generated and may contain mistakes; the official description above is the record.