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

Status: published. Published: 2026-09-23. Updated: 2026-11-06.

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.

## Remediation

- workaround: Avoid using an non-trusted SDK for development/compilation. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (flatpak): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (flatpak): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (flatpak): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (flatpak): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N; source: CNA: redhat

- CVSS 3.1: 9.8 (critical); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: ADP: CISA-ADP

- CISA KEV: No listing in collected sources

- EPSS: 0.44% as of 2026-11-05; percentile 38.06%

- SSVC: exploitation none; automatable yes; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-22

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-96276 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2539418 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://github.com/flatpak/flatpak/security/advisories/GHSA-8qxj-x646-phcm (CNA: redhat)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-96276; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-96276; retrieved 2026-11-06; source updated Not reported

Revision: 673f44e4f9e65b1492dc3d88ddf9dc101fed6dc6041e4ae866b436de94fbbb2a

Canonical: https://y2.dev/cve/CVE-2026-96276

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