The CVE-2025-XXXX vulnerability in Redox OS’s UEFI Safe API arises due to improper handling of null-terminated strings in the `ffi::nstr()` function. This function fails to validate whether the input buffer contains a trailing null byte before processing, leading to a heap buffer overflow when reading beyond the allocated memory. Attackers could exploit this by crafting malicious input that lacks proper termination, causing memory corruption, potential code execution, or system crashes.
The issue stems from Rust’s FFI (Foreign Function Interface) layer, where unchecked pointer dereferencing occurs. Since `ffi::nstr()` is not marked unsafe, developers may unknowingly pass improperly formatted buffers, triggering undefined behavior. The flaw is classified as low severity due to the niche usage of Redox OS and the requirement of local access or specific UEFI interactions for exploitation.
DailyCVE Form:
Platform: Redox OS
Version: Pre-2025 patches
Vulnerability: Heap overflow
Severity: Low
Date: May 6, 2025
What Undercode Say:
Exploitation:
1. Craft a malicious buffer lacking null termination.
2. Pass it to `ffi::nstr()` via UEFI interactions.
3. Trigger heap corruption for denial-of-service or RCE.
Protection:
- Mark `ffi::nstr()` as `unsafe` to enforce caller checks.
2. Validate input buffers for null termination.
- Use Rust’s `CStr` for safer FFI string handling.
Analytics:
- Attack Vector: Local/UEFI-dependent
- Impact: Memory corruption
- Patch Status: Unpatched in older versions
Commands:
// Vulnerable usage (avoid):
let raw_ptr = ...; // No null terminator
let _ = ffi::nstr(raw_ptr);
// Safe alternative:
use std::ffi::CStr;
let cstr = unsafe { CStr::from_ptr(valid_ptr) };
Code Fix:
// Patch: Enforce unsafe and checks
pub unsafe fn nstr(ptr: const u8) -> String {
assert!(!ptr.is_null());
let len = (0..).take_while(|&i| ptr.add(i) != 0).count();
let slice = std::slice::from_raw_parts(ptr, len + 1);
String::from_utf8_lossy(slice).into_owned()
}
Mitigation Steps:
1. Update Redox OS to patched versions.
2. Audit FFI string usage in UEFI modules.
3. Enable Rust’s `[deny(unsafe_code)]` where possible.
Exploit PoC (Conceptual):
let malicious_buf = vec![b'A'; 256]; // No null byte
let _ = unsafe { ffi::nstr(malicious_buf.as_ptr()) }; // Triggers overflow
Log Monitoring:
dmesg | grep "heap corruption"
References:
- GitHub Advisory: GHSA-xxxx-xxxx-xxxx
- Redox OS Commit: Fix `nstr` safety
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
