CVE-2026-97026
Description
Flatpak creates temporary child repository directories under the user cache with world-writable permissions (0777). On multi-user systems with a permissive umask, other local users could read or modify the temporary directory used while installing apps or runtimes, potentially causing installation failures (denial of service); tampered content would fail signature/digest verification rather than being trusted.
Statement
Red Hat estimates the CVSSv3.1 vector of CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L from provided CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N. Requires user interaction and scope remains unchanged.
Mitigation
Set a umask that does not allow other users to write to the cache directory, for example: umask 022.
Note that a umask that does not allow read/exec access by all (for example 027 or 077) will prevent the flatpak-system-helper from reading the temporary directory directly, resulting in falling back to copying the repository inefficiently, with a warning.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.9 | N/A | 3.9 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
If the temporary file can be read by the attacker, sensitive information may be in that file which could be revealed.
Authorization,Other
Technical Impact: Other
If that file can be written to by the attacker, the file might be moved into a place to which the attacker does not have access. This will allow the attacker to gain selective resource access-control privileges.
Integrity,Other
Technical Impact: Other
Depending on the data stored in the temporary file, there is the potential for an attacker to gain an additional input vector which is trusted as non-malicious. It may be possible to make arbitrary changes to data structures, user information, or even process ownership.
Acknowledgements
Red Hat would like to thank AISLE for reporting this issue.
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