{"id":"CVE-2021-21261","state":"PUBLISHED","title":"Flatpak sandbox escape via spawn portal","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.","publishedAt":"2021-01-14T19:40:21.000Z","updatedAt":"2024-08-03T18:09:14.989Z","severity":{"score":7.3,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["flatpak flatpak"],"affected":[{"vendor":"flatpak","product":"flatpak","versions":[{"version":">= 0.11.4, < 1.8.5","status":"affected"},{"version":">= 1.9.0, < 1.10.0","status":"affected"}]}],"references":["https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2","https://github.com/flatpak/flatpak/releases/tag/1.8.5","https://www.debian.org/security/2021/dsa-4830","https://github.com/flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486","https://github.com/flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b","https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4","https://github.com/flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba","https://security.gentoo.org/glsa/202101-21"],"weaknesses":["CWE-74"],"ingestedAt":"2026-10-29T19:47:59.168Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/21xxx/CVE-2021-21261.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2021-21261","state":"PUBLISHED","datePublished":"2021-01-14T19:40:21.000Z","dateUpdated":"2024-08-03T18:09:14.989Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2020-12-22T00:00:00.000Z"},"containers":{"cna":{"title":"Flatpak sandbox escape via spawn portal","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"flatpak","product":"flatpak","versions":[{"version":">= 0.11.4, < 1.8.5","status":"affected"},{"version":">= 1.9.0, < 1.10.0","status":"affected"}]}],"references":[{"url":"https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/flatpak/flatpak/releases/tag/1.8.5","tags":["x_refsource_MISC"]},{"url":"https://www.debian.org/security/2021/dsa-4830","name":"DSA-4830","tags":["vendor-advisory","x_refsource_DEBIAN"]},{"url":"https://github.com/flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486","tags":["x_refsource_MISC"]},{"url":"https://github.com/flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b","tags":["x_refsource_MISC"]},{"url":"https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4","tags":["x_refsource_MISC"]},{"url":"https://github.com/flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba","tags":["x_refsource_MISC"]},{"url":"https://security.gentoo.org/glsa/202101-21","name":"GLSA-202101-21","tags":["vendor-advisory","x_refsource_GENTOO"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"NONE","baseScore":7.3,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-74","description":"CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","dateUpdated":"2021-01-25T02:06:26.000Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa"},"source":{"advisory":"GHSA-4ppf-fxf6-vxg2","discovery":"UNKNOWN"},"x_legacyV4Record":{"CVE_data_meta":{"ASSIGNER":"security-advisories@github.com","ID":"CVE-2021-21261","STATE":"PUBLIC","TITLE":"Flatpak sandbox escape via spawn portal"},"affects":{"vendor":{"vendor_data":[{"product":{"product_data":[{"product_name":"flatpak","version":{"version_data":[{"version_value":">= 0.11.4, < 1.8.5"},{"version_value":">= 1.9.0, < 1.10.0"}]}}]},"vendor_name":"flatpak"}]}},"data_format":"MITRE","data_type":"CVE","data_version":"4.0","description":{"description_data":[{"lang":"eng","value":"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."}]},"impact":{"cvss":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"NONE","baseScore":7.3,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N","version":"3.1"}},"problemtype":{"problemtype_data":[{"description":[{"lang":"eng","value":"CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')"}]}]},"references":{"reference_data":[{"name":"https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2","refsource":"CONFIRM","url":"https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2"},{"name":"https://github.com/flatpak/flatpak/releases/tag/1.8.5","refsource":"MISC","url":"https://github.com/flatpak/flatpak/releases/tag/1.8.5"},{"name":"DSA-4830","refsource":"DEBIAN","url":"https://www.debian.org/security/2021/dsa-4830"},{"name":"https://github.com/flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486","refsource":"MISC","url":"https://github.com/flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486"},{"name":"https://github.com/flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b","refsource":"MISC","url":"https://github.com/flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b"},{"name":"https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4","refsource":"MISC","url":"https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4"},{"name":"https://github.com/flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba","refsource":"MISC","url":"https://github.com/flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba"},{"name":"GLSA-202101-21","refsource":"GENTOO","url":"https://security.gentoo.org/glsa/202101-21"}]},"source":{"advisory":"GHSA-4ppf-fxf6-vxg2","discovery":"UNKNOWN"}}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2","tags":["x_refsource_CONFIRM","x_transferred"]},{"url":"https://github.com/flatpak/flatpak/releases/tag/1.8.5","tags":["x_refsource_MISC","x_transferred"]},{"url":"https://www.debian.org/security/2021/dsa-4830","name":"DSA-4830","tags":["vendor-advisory","x_refsource_DEBIAN","x_transferred"]},{"url":"https://github.com/flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486","tags":["x_refsource_MISC","x_transferred"]},{"url":"https://github.com/flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b","tags":["x_refsource_MISC","x_transferred"]},{"url":"https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4","tags":["x_refsource_MISC","x_transferred"]},{"url":"https://github.com/flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba","tags":["x_refsource_MISC","x_transferred"]},{"url":"https://security.gentoo.org/glsa/202101-21","name":"GLSA-202101-21","tags":["vendor-advisory","x_refsource_GENTOO","x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-03T18:09:14.989Z"}}]}}}