Bug 2539416 (CVE-2026-96275)

Summary: CVE-2026-96275 flatpak: flatpak: Arbitrary write access as root via extra-data extraction
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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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.
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Description OSIDB Bzimport 2026-09-23 14:01:47 UTC 
GHSA-fqx6-vh4p-42cg (https://github.com/flatpak/flatpak/security/advisories/GHSA-fqx6-vh4p-42cg)

Impact: A malicious or compromised Flatpak repository can write attacker-controlled content to arbitrary locations on the host filesystem. On system installs, the write happens as root.

Description: There are two vulnerabilities in extract_extra_data. It resolves files/extra inside the checked-out commit tree using GFile path operations, which follow symlinks. If the files entry in the OSTree commit is a symlink (e.g., files -> /tmp), the downloaded extra-data blobs are written at the symlink target instead. Additionally, extract_extra_data writes downloaded blobs to files/extra/<name> where <name> comes from xa.extra-data-sources in the commit metadata; g_file_get_child resolves .. components, so a name like ../metadata escapes the extra/ directory.

Fixed in 1.18.1 (backports available for 1.16.x). Found by @swick after investigating a report from AISLE in cooperation with Red Hat.
Comment 2 Jon Orris 2026-10-12 02:15:26 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:80498 https://access.redhat.com/errata/RHSA-2026:80498
Comment 3 Jon Orris 2026-10-12 03:09:34 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:80497 https://access.redhat.com/errata/RHSA-2026:80497
Comment 4 Jon Orris 2026-10-12 10:04:45 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:80687 https://access.redhat.com/errata/RHSA-2026:80687