PX4 is an open-source autopilot stack for drones and unmanned vehicles. Versions 1.17.0-rc2 and below are vulnerable to Stack-based Buffer Overflow through the MavlinkLogHandler, and are triggered via MAVLink log request. The LogEntry.filepath buffer is 60 bytes, but the sscanf function parses paths from the log list file with no width specifier, allowing a path longer than 60 characters to overflow the buffer. An attacker with MAVLink link access can trigger this by first creating deeply nested directories via MAVLink FTP, then requesting the log list. The flight controller MAVLink task crashes, losing telemetry and command capability and causing DoS. This issue has been fixed in this commit: https://github.com/PX4/PX4-Autopilot/commit/616b25a280e229c24d5cf12a03dbf248df89c474.
Weakness
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
Potential Mitigations
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
- D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
- Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
- Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
- For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].