CVE-2026-55888
Description
A flaw was found in xdg-desktop-portal. An attacker operating a sandboxed application can bypass isolation boundaries to gain unauthorized access to host files. This issue occurs because the FileChooser interface fails to properly validate filenames before passing them to backend services. Consequently, a malicious application can create and manipulate arbitrary files on the host system, limited only by the permissions of the current user.
Statement
This vulnerability is rated as Important because a rogue or compromised sandboxed client can escape its confinement boundaries and compromise the integrity of host files under the active user account. On Red Hat Enterprise Linux systems running graphical desktop environments with containerized desktop applications, the xdg-desktop-portal service mediates filesystem operations between isolated applications and the host. Insufficient path verification during file export operations enables untrusted sandboxed payloads to write outside designated container boundaries, although exploitation requires an active local user session and cannot grant privileges beyond those of the executing user.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
--- CME Mitigation Guidance (2026-11-02) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to enforce strict filename canonicalization and validation on FileChooser.SaveFiles inputs to prevent directory traversal across backend directory concatenation: upgrade to xdg-desktop-portal 1.22.1 (or the fixed Xdg Desktop Portal builds), which validate filenames provided in the files option of FileChooser.SaveFiles to ensure they do not traverse directories, closing all 2 injection vectors (crafted filenames via FileChooser.SaveFiles 'files' option, path traversal during directory concatenation in portal backend). Until patched, this is only a concern on Linux desktop environments running sandboxed applications with D-Bus access to xdg-desktop-portal — non-Linux deployments and headless server environments without graphical desktop portals are unaffected — so restrict untrusted sandboxed applications from communicating with the portal D-Bus interface and exercise caution when interacting with file saving prompts. As a compensating measure, audit filesystem system calls using auditd to log and alert on unexpected file creation outside sandboxed application directories, restrict backend filesystem writes strictly to the explicitly selected directory to block traversal outside chosen folder boundaries, run SELinux in enforcing mode to restrict unauthorized file creation across host domains, apply Landlock filesystem sandboxing to restrict portal service write boundaries across host directories, deploy EDR agents to detect anomalous host file creation and path traversal behavior initiated via the portal service, and implement Falco or eBPF runtime security probes to detect anomalous host file write operations initiated by portal backend processes. These controls limit blast radius and contain exploitation, but they do not fix the underlying unvalidated-filename path traversal defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-1301 Path Traversal Prevention (Canonicalization) (high)
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 | 8.2 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | Required | N/A | N/A |
| Scope | Changed | N/A | N/A |
| Confidentiality | High | N/A | N/A |
| Integrity Impact | High | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.
Integrity
Technical Impact: Modify Files or Directories
The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.
Confidentiality
Technical Impact: Read Files or Directories
The attacker may be able to read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of protection mechanisms such as authentication, it has the potential to lock out product users.
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