Gvfs: sftp: heap-based buffer overflow in read_reply()

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.

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may execute code or commands in the affected security context.