GHSA-2x3r-hwv5-p32x

### Summary

This affects AES-256-GCM and AES-128-GCM in Deno, introduced by commit [0d1beed](https://github.com/denoland/deno/commit/0d1beed). Specifically, the authentication tag is not being validated. This means tampered ciphertexts or incorrect keys might not be detected, which breaks the guarantees expected from AES-GCM. Older versions of Deno correctly threw errors in such cases, as does Node.js.

Without authentication tag verification, AES-GCM degrades to essentially CTR mode, removing integrity protection. Authenticated data set with set_aad is also affected, as it is incorporated into the GCM hash (ghash) but this too is not validated, rendering AAD checks ineffective.

### PoC

```ts import { Buffer } from "node:buffer"; import { createCipheriv, createDecipheriv, randomBytes, scrypt, } from "node:crypto";

type Encrypted = { salt: string; iv: string; enc: string; authTag: string; };

const deriveKey = (key: string, salt: Buffer) => new Promise<Buffer>((res, rej) => scrypt(key, salt, 32, (err, k) => { if (err) rej(err); else res(k); }) );

async function encrypt(text: string, key: string): Promise<Encrypted> { const salt = randomBytes(32); const k = await deriveKey(key, salt);

const iv = randomBytes(16); const enc = createCipheriv("aes-256-gcm", k, iv); const ciphertext = enc.update(text, "binary", "binary") + enc.final("binary");

return { salt: salt.toString("binary"), iv: iv.toString("binary"), enc: ciphertext, authTag: enc.getAuthTag().toString("binary"), }; }

async function decrypt(enc: Encrypted, key: string) { const k = await deriveKey(key, Buffer.from(enc.salt, "binary")); const dec = createDecipheriv("aes-256-gcm", k, Buffer.from(enc.iv, "binary"));

const out = dec.update(enc.enc, "binary", "binary"); dec.setAuthTag(Buffer.from(enc.authTag, "binary")); return out + dec.final("binary"); }

const test = await encrypt("abcdefghi", "key"); test.enc = ""; console.log(await decrypt(test, "")); // no error ```

### Impact

While discovered through experimentation, authentication failures that should raise errors may be silently ignored.