{"api_version":"1","generated_at":"2026-04-12T00:29:53+00:00","cve":"CVE-2021-21261","urls":{"html":"https://cve.report/CVE-2021-21261","api":"https://cve.report/api/cve/CVE-2021-21261.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2021-21261","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-21261"},"summary":{"title":"CVE-2021-21261","description":"Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. A bug was discovered in the `flatpak-portal` service that can allow sandboxed applications to execute arbitrary code on the host system (a sandbox escape). This sandbox-escape bug is present in versions from 0.11.4 and before fixed versions 1.8.5 and 1.10.0. The Flatpak portal D-Bus service (`flatpak-portal`, also known by its D-Bus service name `org.freedesktop.portal.Flatpak`) allows apps in a Flatpak sandbox to launch their own subprocesses in a new sandbox instance, either with the same security settings as the caller or with more restrictive security settings. For example, this is used in Flatpak-packaged web browsers such as Chromium to launch subprocesses that will process untrusted web content, and give those subprocesses a more restrictive sandbox than the browser itself. In vulnerable versions, the Flatpak portal service passes caller-specified environment variables to non-sandboxed processes on the host system, and in particular to the `flatpak run` command that is used to launch the new sandbox instance. A malicious or compromised Flatpak app could set environment variables that are trusted by the `flatpak run` command, and use them to execute arbitrary code that is not in a sandbox. As a workaround, this vulnerability can be mitigated by preventing the `flatpak-portal` service from starting, but that mitigation will prevent many Flatpak apps from working correctly. This is fixed in versions 1.8.5 and 1.10.0.","state":"PUBLIC","assigner":"security-advisories@github.com","published_at":"2021-01-14 20:15:00","updated_at":"2021-01-27 19:34:00"},"problem_types":["CWE-74"],"metrics":[],"references":[{"url":"https://www.debian.org/security/2021/dsa-4830","name":"DSA-4830","refsource":"DEBIAN","tags":["Third Party Advisory"],"title":"Debian -- Security Information -- DSA-4830-1 flatpak","mime":"text/html","httpstatus":"200","archivestatus":"200"},{"url":"https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4","name":"https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4","refsource":"MISC","tags":["Patch","Third Party Advisory"],"title":"portal: Convert --env in extra-args into --env-fd · flatpak/flatpak@aeb6a7a · 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A bug was discovered in the `flatpak-portal` service that can allow sandboxed applications to execute arbitrary code on the host system (a sandbox escape). This sandbox-escape bug is present in versions from 0.11.4 and before fixed versions 1.8.5 and 1.10.0. The Flatpak portal D-Bus service (`flatpak-portal`, also known by its D-Bus service name `org.freedesktop.portal.Flatpak`) allows apps in a Flatpak sandbox to launch their own subprocesses in a new sandbox instance, either with the same security settings as the caller or with more restrictive security settings. For example, this is used in Flatpak-packaged web browsers such as Chromium to launch subprocesses that will process untrusted web content, and give those subprocesses a more restrictive sandbox than the browser itself. In vulnerable versions, the Flatpak portal service passes caller-specified environment variables to non-sandboxed processes on the host system, and in particular to the `flatpak run` command that is used to launch the new sandbox instance. A malicious or compromised Flatpak app could set environment variables that are trusted by the `flatpak run` command, and use them to execute arbitrary code that is not in a sandbox. As a workaround, this vulnerability can be mitigated by preventing the `flatpak-portal` service from starting, but that mitigation will prevent many Flatpak apps from working correctly. This is fixed in versions 1.8.5 and 1.10.0.","Type":"Description","Title":null},{"CveYear":"2021","CveId":"21261","Ordinal":"2","NoteData":"2021-01-14","Type":"Other","Title":"Published"},{"CveYear":"2021","CveId":"21261","Ordinal":"3","NoteData":"2021-01-24","Type":"Other","Title":"Modified"}]}}}