flatpak: UNIX Symbolic Link (Symlink) Following
CVE-2026-34078 is a critical-severity UNIX symbolic link (symlink) following vulnerability in flatpak, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected flatpak versions: < 1.16.4. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.71% chance of exploitation within 30 days, higher than 78% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of flatpak you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.3 | Critical | CNA (github.com) |
| CVSS 3.1 | 10.0 | Critical | NVD |
| CVSS 3.1 | 9.0 | Critical | CNA |
Official description
Flatpak is a Linux application sandboxing and distribution framework. Prior to 1.16.4, the Flatpak portal accepts paths in the sandbox-expose options which can be app-controlled symlinks pointing at arbitrary paths. Flatpak run mounts the resolved host path in the sandbox. This gives apps access to all host files and can be used as a primitive to gain code execution in the host context. This vulnerability is fixed in 1.16.4.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: UNIX Symbolic Link (Symlink) Following
The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
How developers prevent this class of flaw
- Symbolic link attacks often occur when a program creates a tmp directory that stores files/links. Access to the directory should be restricted to the program as to prevent attackers from manipulating the files.
- Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
More UNIX Symbolic Link (Symlink) Following vulnerabilities (CWE-61)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- openwall.com/lists/oss-security/2026/04/09/8Mailing List, Third Party Advisory
- openwall.com/lists/oss-security/2026/04/10/14Mailing List, Third Party Advisory
Other references
- access.redhat.com/errata/RHSA-2026:21755
- access.redhat.com/errata/RHSA-2026:21756
- access.redhat.com/errata/RHSA-2026:21757
- access.redhat.com/errata/RHSA-2026:23417
- access.redhat.com/errata/RHSA-2026:23418
- access.redhat.com/errata/RHSA-2026:23419
- access.redhat.com/errata/RHSA-2026:23420
- access.redhat.com/errata/RHSA-2026:25068
- access.redhat.com/errata/RHSA-2026:25381
- access.redhat.com/errata/RHSA-2026:30901
- access.redhat.com/errata/RHSA-2026:35843
- access.redhat.com/security/cve/CVE-2026-34078
- bugzilla.redhat.com/show_bug.cgi?id=2456276
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34078.json
Other vulnerabilities in flatpak
- 7.2 High severity
- 7.4 High severity
- 7.4 High severity
- 7.5 High severity
- 10.0 Critical severity
- 8.4 High severity
Recent UNIX Symbolic Link (Symlink) Following vulnerabilities
- 7.3 High severity
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
- 7.5 High severity
- 7.1 High severity
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