Flatpak Symlink toctou

Summaryinfo

A vulnerability classified as problematic has been found in Flatpak. Affected is an unknown function of the component Symlink. The manipulation leads to toctou. This vulnerability is referenced as CVE-2026-76925. The attack can only be performed from a local environment. No exploit is available.

Detailsinfo

A vulnerability was found in Flatpak (version now known) and classified as problematic. This issue affects some unknown processing of the component Symlink. The manipulation with an unknown input leads to a toctou vulnerability. Using CWE to declare the problem leads to CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

A flaw was found in Flatpak. A Time-of-check to time-of-use (TOCTOU) race condition exists in the `org.freedesktop.Flatpak.SystemHelper` component. This vulnerability occurs because a privileged `chmod` operation executes before the OSTree repository validation within the `Deploy()` function. An attacker can exploit this timing window to redirect symlinks to arbitrary files, potentially leading to unauthorized file manipulation or information disclosure.

The identification of this vulnerability is CVE-2026-76925. The exploitation is known to be easy. An attack has to be approached locally. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 342817 (Linux Distros Unpatched Vulnerability : CVE-2026-76925), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at Tenable (342817). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

• Flatpak

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion