From b91744fa5cd2a0c9471978f8a6db4436c7b1b6f1 Mon Sep 17 00:00:00 2001
From: Sergio Barrio <sergio.barrio@datadoghq.com>
Date: Tue, 22 Sep 2026 14:31:33 +0200
Subject: [PATCH] Fix String(value) throwing when encoding attributes

---
 .../__tests__/attributesEncoding.test.ts      | 25 +++++++++++++++++++
 .../sdk/AttributesEncoding/defaultEncoders.ts |  8 ++++--
 .../src/sdk/AttributesEncoding/helpers.ts     | 12 ++++-----
 .../core/src/sdk/AttributesEncoding/utils.ts  |  8 ++++++
 4 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/packages/core/src/sdk/AttributesEncoding/__tests__/attributesEncoding.test.ts b/packages/core/src/sdk/AttributesEncoding/__tests__/attributesEncoding.test.ts
index 06a292431..87a553d7c 100644
--- a/packages/core/src/sdk/AttributesEncoding/__tests__/attributesEncoding.test.ts
+++ b/packages/core/src/sdk/AttributesEncoding/__tests__/attributesEncoding.test.ts
@@ -41,6 +41,31 @@ describe('encodeAttributes', () => {
         expect(warn).toHaveBeenCalled();
     });
 
+    it('drops a null-prototype object without throwing', () => {
+        expect(() =>
+            encodeAttributes({ bad: Object.create(null) })
+        ).not.toThrow();
+        expect(warn).toHaveBeenCalled();
+    });
+
+    it('drops a value whose toString throws without throwing', () => {
+        const bad = {
+            toString() {
+                throw new Error('boom');
+            }
+        };
+        Object.setPrototypeOf(bad, null);
+        expect(() => encodeAttributes({ bad })).not.toThrow();
+        expect(warn).toHaveBeenCalled();
+    });
+
+    it('drops a null-prototype object nested in an array without throwing', () => {
+        expect(() =>
+            encodeAttributes({ bad: [Object.create(null)] })
+        ).not.toThrow();
+        expect(warn).toHaveBeenCalled();
+    });
+
     it('drops unsupported root function', () => {
         const result = encodeAttributes(() => {});
         expect(result).toEqual({});
diff --git a/packages/core/src/sdk/AttributesEncoding/defaultEncoders.ts b/packages/core/src/sdk/AttributesEncoding/defaultEncoders.ts
index b3634859a..f3dfc240f 100644
--- a/packages/core/src/sdk/AttributesEncoding/defaultEncoders.ts
+++ b/packages/core/src/sdk/AttributesEncoding/defaultEncoders.ts
@@ -16,7 +16,7 @@ import {
 } from './errorUtils';
 import { encodeAttributesInPlace, sanitizeForJson } from './helpers';
 import type { AttributeEncoder, Encodable } from './types';
-import { warn } from './utils';
+import { safeToString, warn } from './utils';
 
 /** Primitives: keep them explicit so the full pipeline is used uniformly. */
 export const stringEncoder: AttributeEncoder<string> = {
@@ -165,7 +165,11 @@ export const mapEncoder: AttributeEncoder<Map<unknown, unknown>> = {
                     value: sanitizeForJson(v, allEncoders)
                 });
             } catch (err) {
-                warn(`Failed to encode Map key: ${k}. ERROR: ${String(err)}`);
+                warn(
+                    `Failed to encode Map key: ${safeToString(
+                        k
+                    )}. ERROR: ${safeToString(err)}`
+                );
             }
         }
 
diff --git a/packages/core/src/sdk/AttributesEncoding/helpers.ts b/packages/core/src/sdk/AttributesEncoding/helpers.ts
index c47762312..33c439874 100644
--- a/packages/core/src/sdk/AttributesEncoding/helpers.ts
+++ b/packages/core/src/sdk/AttributesEncoding/helpers.ts
@@ -5,7 +5,7 @@
  */
 
 import type { AttributeEncoder, Encodable } from './types';
-import { formatPathForLog, isPlainObject, warn } from './utils';
+import { formatPathForLog, isPlainObject, safeToString, warn } from './utils';
 
 const MAX_ATTRIBUTES = 256;
 
@@ -69,7 +69,7 @@ export function encodeAttributesInPlace(
             warn(
                 `Dropped unsupported value in array at '${formatPathForLog(
                     path
-                )}': ${String(v)}`
+                )}': ${safeToString(v)}`
             );
             return undefined;
         };
@@ -94,9 +94,9 @@ export function encodeAttributesInPlace(
 
     // Unsupported
     warn(
-        `Dropped unsupported value at '${formatPathForLog(path)}': ${String(
-            value
-        )}`
+        `Dropped unsupported value at '${formatPathForLog(
+            path
+        )}': ${safeToString(value)}`
     );
 }
 
@@ -138,7 +138,7 @@ export function applyEncoders(
                 return enc.encode(value as never);
             }
         } catch (err) {
-            warn(`Encoder error: ${String(err)}`);
+            warn(`Encoder error: ${safeToString(err)}`);
             return undefined;
         }
     }
diff --git a/packages/core/src/sdk/AttributesEncoding/utils.ts b/packages/core/src/sdk/AttributesEncoding/utils.ts
index 1187828d6..a87f73982 100644
--- a/packages/core/src/sdk/AttributesEncoding/utils.ts
+++ b/packages/core/src/sdk/AttributesEncoding/utils.ts
@@ -11,6 +11,14 @@ export function warn(text: string) {
     InternalLog.log(`[ATTRIBUTES] ${text}`, SdkVerbosity.WARN);
 }
 
+export function safeToString(value: unknown): string {
+    try {
+        return String(value);
+    } catch {
+        return Object.prototype.toString.call(value);
+    }
+}
+
 export function isPlainObject(v: unknown): v is Record<string, unknown> {
     return !!v && typeof v === 'object' && (v as any).constructor === Object;
 }