CVE-2026-84267 Gvfs: sftp: uninitialized heap disclosure in read_string()

Description

A flaw was found in the SFTP backend in gvfs. When mounting a share, a malicious SFTP server can cause read_string() to allocate a buffer with a certain length but the function does not verify that the buffer is completely filled, leaving the remainder of the buffer containing uninitialized heap contents. If the server sends a short FXP_HANDLE reply, these uninitialized bytes are taken as the file handle. The client will then echo these uninitialized bytes back to the server on all subsequent requests using that handle. With a length of 128 bytes, this issue allows the malicious server to deterministically read uninitialized heap memory from the gvfsd-sftp process, leaking its heap base and the load address of the libgio library, resulting in a deterministic defeat of Address Space Layout Randomization (ASLR).

Exploitable à distance par le réseau, sans compte et si un utilisateur effectue une action ; l’impact sur les données ou le service reste limité.

Vecteur d’attaque

Réseau

Complexité

Faible

Privilèges requis

Aucun

Interaction

Requise

Portée

Inchangée

Confidentialité

Faible

Intégrité

Aucun

Disponibilité

Aucun

Produits et versions touchés