fix(native): validate buffer attachment paths

CHANGELOG.md

@@ -24,6 +24,7 @@
 - macOS: prevent out-of-bounds reads while parsing Mach-O load commands. ([#2065](https://github.com/getsentry/sentry-native/pull/2065))
 - Prevent out-of-bounds reads when parsing JSON numbers from length-delimited buffers. ([#2067](https://github.com/getsentry/sentry-native/pull/2067))
 - Native/Windows: resolve the WER module relative to `handler_path`, so it is found when the crash handler is installed outside the executable's directory. ([#2073](https://github.com/getsentry/sentry-native/pull/2073))
+- Native: prevent buffer attachments from being written outside their UUID run directory. ([#2072](https://github.com/getsentry/sentry-native/pull/2072))
 
 **Thank you**:
 

src/backends/sentry_backend_native.c

@@ -1260,6 +1260,11 @@ ensure_attachment_path(sentry_attachment_t *attachment)
         return false;
     }
 
+    const char *filename = sentry__path_filename(attachment->filename);
+    if (sentry__string_empty(filename)) {
+        return false;
+    }
+
     // Generate UUID for unique path
     sentry_uuid_t uuid = sentry_uuid_new_v4();
     char uuid_str[37];
@@ -1272,18 +1277,24 @@ ensure_attachment_path(sentry_attachment_t *attachment)
         }
     }
 
-    if (!base_path || sentry__path_create_dir_all(base_path) != 0) {
-        sentry__path_free(base_path);
+    if (!base_path) {
         return false;
     }
 
-    sentry_path_t *old_path = attachment->path;
-    attachment->path = sentry__path_join_str(
-        base_path, sentry__path_filename(attachment->filename));
+    sentry_path_t *path = sentry__path_join_str(base_path, filename);
+    sentry_path_t *parent = path ? sentry__path_dir(path) : NULL;
+    bool valid = parent && sentry__path_eq(parent, base_path);
+    sentry__path_free(parent);
+    if (!valid || sentry__path_create_dir_all(base_path) != 0) {
+        sentry__path_free(path);
+        sentry__path_free(base_path);
+        return false;
+    }
 
     sentry__path_free(base_path);
-    sentry__path_free(old_path);
-    return attachment->path != NULL;
+    sentry__path_free(attachment->path);
+    attachment->path = path;
+    return true;
 }
 
 static void