OESA-2026-3824

Gvfs is a userspace virtual filesystem implementation for GIO (a library available in GLib). It comes with a set of backends, including trash support, SFTP, SMB, HTTP, DAV, and many others. Gvfs also contains modules for GIO that implement volume monitors and persistent metadata storage.

Security Fix(es):

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).(CVE-2026-84267)

A flaw was found in the SFTP backend in gvfs. When mounting a share and reading a file, a malicious SFTP server can cause read_reply() to process a length that exceeds the size requested by the client. The function does not verify the server-provided length against the allocated buffer size, causing the operation to write past the intended boundaries. This issue allows a malicious server to corrupt adjacent heap memory in the gvfsd-sftp process, resulting in a denial of service as the process aborts upon detecting the heap corruption or potentially allowing arbitrary code execution.(CVE-2026-84268)

A flaw was found in the AFP backend in gvfs. When mounting a share, a malicious AFP server can cause the DSI read path to process a length that exceeds the size requested by the client. The function does not verify the server-provided length against the pre-sized reply buffer, causing the operation to access past the intended boundaries. This issue allows a malicious server to overflow a heap buffer and crash the gvfsd-afp process, resulting in a denial of service.(CVE-2026-84269)

A flaw was found in the MTP backend in gvfs. When reading a file from a mounted MTP device, do_read() in gvfsbackendmtp.c trusts the data length returned by the device without limiting it to the original size requested by the client. If a malicious MTP device responds with more bytes than requested, this unrestricted length is passed directly to memcpy(). This causes the operation to read memory outside the intended boundaries. This allows an attacker who plugs in a malicious MTP device to cause a segmentation fault when a file is read and crash the gvfsd-mtp process, resulting in a denial of service.(CVE-2026-84270)