{"cve":"CVE-2021-21381","nvd":{"published":"2021-03-11T17:15:12.703","modified":"2026-06-17T03:35:27.157","status":"Modified","description":"Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In Flatpack since version 0.9.4 and before version 1.10.2 has a vulnerability in the \"file forwarding\" feature which can be used by an attacker to gain access to files that would not ordinarily be allowed by the app's permissions. By putting the special tokens `@@` and/or `@@u` in the Exec field of a Flatpak app's .desktop file, a malicious app publisher can trick flatpak into behaving as though the user had chosen to open a target file with their Flatpak app, which automatically makes that file available to the Flatpak app. This is fixed in version 1.10.2. A minimal solution is the first commit \"`Disallow @@ and @@U usage in desktop files`\". The follow-up commits \"`dir: Reserve the whole @@ prefix`\" and \"`dir: Refuse to export .desktop files with suspicious uses of @@ tokens`\" are recommended, but not strictly required. As a workaround, avoid installing Flatpak apps from untrusted sources, or check the contents of the exported `.desktop` files in `exports/share/applications/*.desktop` (typically `~/.local/share/flatpak/exports/share/applications/*.desktop` and `/var/lib/flatpak/exports/share/applications/*.desktop`) to make sure that literal filenames do not follow `@@` or `@@u`.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N","score":8.2},"cwes":["CWE-74"],"references":["https://github.com/flatpak/flatpak/commit/8279c5818425b6812523e3805bbe242fb6a5d961","https://github.com/flatpak/flatpak/commit/a7401e638bf0c03102039e216ab1081922f140ae","https://github.com/flatpak/flatpak/commit/eb7946bb6248923d8c90fe9b84425fef97ae580d","https://github.com/flatpak/flatpak/pull/4156","https://github.com/flatpak/flatpak/releases/tag/1.10.2"],"products":["debian:debian_linux","fedoraproject:fedora","flatpak:flatpak"],"source":"nvd","synced_at":"2026-10-19T21:15:50.279857260+00:00"},"epss":{"cve":"CVE-2021-21381","score":0.01546,"percentile":0.74999,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}