diff --git a/packages/lib/server-only/webhooks/is-private-url.test.ts b/packages/lib/server-only/webhooks/is-private-url.test.ts
index 841ed7938..d0c122818 100644
--- a/packages/lib/server-only/webhooks/is-private-url.test.ts
+++ b/packages/lib/server-only/webhooks/is-private-url.test.ts
@@ -81,13 +81,20 @@ describe('isPrivateUrl', () => {
       expect(isPrivateUrl('http://[fd12::1]')).toBe(true);
     });
 
-    it('should not catch IPv4-mapped IPv6 in URL form (URL parser normalizes to hex)', () => {
-      // new URL() normalizes "::ffff:127.0.0.1" to "::ffff:7f00:1" which none
-      // of the checks handle. This is fine because dns.lookup never returns
-      // IPv4-mapped addresses — it returns plain IPv4 (family: 4) instead.
-      expect(isPrivateUrl('http://[::ffff:127.0.0.1]')).toBe(false);
-      expect(isPrivateUrl('http://[::ffff:10.0.0.1]')).toBe(false);
+    it('should detect private IPv4-mapped IPv6 addresses (URL parser normalizes to hex)', () => {
+      // new URL() normalizes "::ffff:127.0.0.1" to the hex form "::ffff:7f00:1",
+      // so the embedded IPv4 must be decoded and re-checked. Otherwise a literal
+      // host such as http://[::ffff:127.0.0.1] bypasses every dotted-decimal
+      // check above (SSRF, see #2901).
+      expect(isPrivateUrl('http://[::ffff:127.0.0.1]')).toBe(true);
+      expect(isPrivateUrl('http://[::ffff:10.0.0.1]')).toBe(true);
+      expect(isPrivateUrl('http://[::ffff:192.168.0.1]')).toBe(true);
+      expect(isPrivateUrl('http://[::ffff:169.254.169.254]')).toBe(true);
+    });
+
+    it('should still allow public IPv4-mapped IPv6 addresses', () => {
       expect(isPrivateUrl('http://[::ffff:8.8.8.8]')).toBe(false);
+      expect(isPrivateUrl('http://[::ffff:1.1.1.1]')).toBe(false);
     });
   });
 
diff --git a/packages/lib/server-only/webhooks/is-private-url.ts b/packages/lib/server-only/webhooks/is-private-url.ts
index 38f531ee0..c75966792 100644
--- a/packages/lib/server-only/webhooks/is-private-url.ts
+++ b/packages/lib/server-only/webhooks/is-private-url.ts
@@ -69,11 +69,25 @@ export const isPrivateUrl = (url: string): boolean => {
       }
     }
 
-    // IPv4-mapped IPv6 (e.g. ::ffff:127.0.0.1)
-    const v4Mapped = normalizedHost.match(/^::ffff:(\d+\.\d+\.\d+\.\d+)$/i);
+    // IPv4-mapped IPv6, dotted form (e.g. ::ffff:127.0.0.1)
+    const v4MappedDotted = normalizedHost.match(/^::ffff:(\d+\.\d+\.\d+\.\d+)$/i);
 
-    if (v4Mapped) {
-      return isPrivateUrl(`http://${v4Mapped[1]}`);
+    if (v4MappedDotted) {
+      return isPrivateUrl(`http://${v4MappedDotted[1]}`);
+    }
+
+    // IPv4-mapped IPv6, hex form (e.g. ::ffff:7f00:1). `new URL()` normalizes the
+    // dotted form above to this, so it must be decoded to the embedded IPv4 as
+    // well - otherwise a literal host such as `http://[::ffff:127.0.0.1]` slips
+    // through every dotted-decimal check above (SSRF, see #2901).
+    const v4MappedHex = normalizedHost.match(/^::ffff:([0-9a-f]{1,4}):([0-9a-f]{1,4})$/i);
+
+    if (v4MappedHex) {
+      const high = parseInt(v4MappedHex[1], 16);
+      const low = parseInt(v4MappedHex[2], 16);
+      const ipv4 = [high >> 8, high & 0xff, low >> 8, low & 0xff].join('.');
+
+      return isPrivateUrl(`http://${ipv4}`);
     }
 
     return false;