CVE-2026-84267

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).

To exploit this issue, an attacker needs a user to connect to a malicious SFTP share (for example, by clicking a crafted sftp:// link or intercepting an unverified connection), limiting its exposure. Furthermore, the direct security impact of this flaw is limited to an information disclosure of specific memory contents, specifically the heap base of the gvfsd-sftp process and the load address of the libgio library but it does not expose any user data. For these reasons, this vulnerability has been rated with a moderate severity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this vulnerability, do not connect to untrusted SFTP servers.