diff --git a/server_manager/src/core/atomic_io.rs b/server_manager/src/core/atomic_io.rs
index 07e2030..fde1718 100644
--- a/server_manager/src/core/atomic_io.rs
+++ b/server_manager/src/core/atomic_io.rs
@@ -15,6 +15,7 @@ use std::os::unix::fs::OpenOptionsExt;
 /// 4. Synchronizes to disk via `fsync` (`sync_all`).
 /// 5. Atomically renames the temporary file to the destination path.
 pub fn atomic_write<P: AsRef<Path>>(path: P, content: &[u8], mode: u32) -> Result<()> {
+    crate::core::validate::validate_safe_path(&path)?;
     let dest = path.as_ref();
     let parent = dest.parent().unwrap_or_else(|| Path::new("."));
     if !parent.as_os_str().is_empty() {
diff --git a/server_manager/src/core/journal.rs b/server_manager/src/core/journal.rs
index e4adc45..512a62e 100644
--- a/server_manager/src/core/journal.rs
+++ b/server_manager/src/core/journal.rs
@@ -66,6 +66,7 @@ impl Journal {
 
     /// Opens or creates the journal file with 0600 permissions.
     pub fn open_or_create<P: AsRef<Path>>(path: P) -> Result<Self> {
+        crate::core::validate::validate_safe_path(&path)?;
         let target = path.as_ref();
         let parent = target.parent().unwrap_or_else(|| Path::new("."));
         if !parent.as_os_str().is_empty() {
diff --git a/server_manager/src/core/lock.rs b/server_manager/src/core/lock.rs
index fb3e8cd..c11171d 100644
--- a/server_manager/src/core/lock.rs
+++ b/server_manager/src/core/lock.rs
@@ -15,6 +15,7 @@ impl ProcessLock {
     /// Attempts to acquire an exclusive lock on the specified path.
     /// If `non_blocking` is true and the lock is already held, returns an error immediately.
     pub fn acquire<P: AsRef<Path>>(path: P, non_blocking: bool) -> Result<Self> {
+        crate::core::validate::validate_safe_path(&path)?;
         let target = path.as_ref();
         let parent = target.parent().unwrap_or_else(|| Path::new("."));
         if !parent.as_os_str().is_empty() {
diff --git a/server_manager/src/core/validate.rs b/server_manager/src/core/validate.rs
index 9c4898e..5233e8c 100644
--- a/server_manager/src/core/validate.rs
+++ b/server_manager/src/core/validate.rs
@@ -139,10 +139,25 @@ pub fn validate_ip(ip_str: &str) -> Result<IpAddr> {
         .map_err(|_| anyhow::anyhow!("Validation error: invalid IP address '{}'", ip_str))
 }
 
-/// Validates that a path does not contain directory traversal sequences (`..`).
+/// Validates that a path does not contain directory traversal sequences (`..`), NUL bytes, or control characters.
 pub fn validate_safe_path<P: AsRef<Path>>(path: P) -> Result<P> {
     let p = path.as_ref();
-    let normalized = p.to_string_lossy().replace('\\', "/");
+    let path_str = p.to_string_lossy();
+    if path_str.contains('\0') {
+        bail!(
+            "Validation error: NUL byte forbidden in path '{}'",
+            p.display()
+        );
+    }
+    for c in path_str.chars() {
+        if c.is_ascii_control() {
+            bail!(
+                "Validation error: control character forbidden in path '{}'",
+                p.display()
+            );
+        }
+    }
+    let normalized = path_str.replace('\\', "/");
     let norm_path = Path::new(&normalized);
     for comp in norm_path.components() {
         if comp == Component::ParentDir {
diff --git a/server_manager/tests/contract_atomic_io.rs b/server_manager/tests/contract_atomic_io.rs
index 1c96f20..1ff8900 100644
--- a/server_manager/tests/contract_atomic_io.rs
+++ b/server_manager/tests/contract_atomic_io.rs
@@ -31,6 +31,12 @@ fn test_atomic_write_creates_file_with_content() {
     let _ = fs::remove_dir_all(&temp_dir);
 }
 
+#[test]
+fn test_atomic_write_rejects_unsafe_path() {
+    let bytes = b"test payload";
+    assert!(atomic_write("../unsafe_atomic_write.tmp", bytes, 0o600).is_err());
+}
+
 #[test]
 fn test_atomic_write_overwrites_existing_file() {
     let temp_dir = std::env::temp_dir().join(format!(
diff --git a/server_manager/tests/contract_input_validation.rs b/server_manager/tests/contract_input_validation.rs
index 7b9da2d..e7ab059 100644
--- a/server_manager/tests/contract_input_validation.rs
+++ b/server_manager/tests/contract_input_validation.rs
@@ -120,4 +120,10 @@ fn test_validate_safe_path_extended_traversal() {
     assert!(validate_safe_path(Path::new("..\\secret")).is_err());
     assert!(validate_safe_path(Path::new("..")).is_err());
     assert!(validate_safe_path(Path::new(".")).is_ok());
+
+    // NUL byte & control characters
+    assert!(validate_safe_path(Path::new("config.yaml\0.bak")).is_err());
+    assert!(validate_safe_path(Path::new("config\nfile.txt")).is_err());
+    assert!(validate_safe_path(Path::new("config\rfile.txt")).is_err());
+    assert!(validate_safe_path(Path::new("config\tfile.txt")).is_err());
 }
diff --git a/server_manager/tests/contract_journal.rs b/server_manager/tests/contract_journal.rs
index 6ed31d8..1691380 100644
--- a/server_manager/tests/contract_journal.rs
+++ b/server_manager/tests/contract_journal.rs
@@ -45,6 +45,11 @@ fn test_journal_creation_and_append() {
     let _ = fs::remove_dir_all(&temp_dir);
 }
 
+#[test]
+fn test_journal_open_or_create_rejects_unsafe_path() {
+    assert!(Journal::open_or_create("../unsafe_journal.jsonl").is_err());
+}
+
 #[test]
 fn test_journal_compensatory_rollback_in_reverse_order() {
     let temp_dir = std::env::temp_dir().join(format!(
diff --git a/server_manager/tests/contract_locking.rs b/server_manager/tests/contract_locking.rs
index 49bbbc3..254dd25 100644
--- a/server_manager/tests/contract_locking.rs
+++ b/server_manager/tests/contract_locking.rs
@@ -39,3 +39,8 @@ fn test_process_lock_acquisition_and_mutual_exclusion() {
 
     let _ = fs::remove_dir_all(&temp_dir);
 }
+
+#[test]
+fn test_process_lock_rejects_unsafe_path() {
+    assert!(ProcessLock::acquire("../unsafe.lock", true).is_err());
+}