CVE-2026-96276: Flatpak: flatpak: arbitrary write in host context via flatpak build-init

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-23 · updated 2026-09-27
Weakness: CWE-22

Description

If a malicious SDK container declares an extension point with a crafted `directory` path, and a developer runs `flatpak build-init --writable-sdk --sdk-extension` with that SDK, attacker-chosen files could be written outside the working directory, since the target path is resolved via a function that allows `..` traversal.

Affected products

Red Hat Enterprise Linux 10: all versions
Red Hat Enterprise Linux 7: all versions
Red Hat Enterprise Linux 8: all versions
Red Hat Enterprise Linux 9: all versions

References

https://access.redhat.com/security/cve/CVE-2026-96276
https://bugzilla.redhat.com/show_bug.cgi?id=2539418
https://github.com/flatpak/flatpak/security/advisories/GHSA-8qxj-x646-phcm

Get alerted when CVE-2026-96276 or the next vulnerability affects your stack