Forge: AES-GCM authentication bypass via unvalidated tagLength option

Summary The AES-GCM mode in forge.cipher does not validate the tagLength option passed to start(). With a tagLength of 0 or a value that converts to 0 (such as null, false, '' or '0'), the authentication tag is empty, and decipher.finish() returns true for any ciphertext and additional data when the supplied tag is empty or missing. Fixed in node-forge 1.4.1. Details modes.gcm.prototype.start() in lib/cipherModes.js stored the tagLength option without validation, and lib/cipher.js documented it as accepting "0-128". After processing the data, afterFinish() truncates the 16-byte tag with truncate(16 % (tagLength / 8)). For a tagLength that converts to 0, this is 16 % 0 = NaN, and truncating by NaN empties the tag. On decryption, the start-time check that the supplied tag has tagLength / 8 bytes passes for an empty tag, and the final tag comparison compares two empty strings, so decipher.finish() returns true for any ciphertext and additional data. NIST SP 800-38D section 5.2.1.2 allows only tag lengths of 128, 120, 112, 104 and 96 bits, plus 64 and 32 bits for certain applications. The fix validates tagLength in start(), for both encryption and decryption. A missing, null or…

curl https://cve.zerocrew.in/api/cve/CVE-2026-119186