peass-ng/PEASS-ng · error · ArgumentException

invalid parameters passed to GCM

Error message

invalid parameters passed to GCM

What it means

A fallback branch in GcmBlockCipher.Init: the supplied cipher parameters object was neither AeadParameters nor ParametersWithIV, so the cipher cannot obtain a nonce or key. It fires when callers pass e.g. a raw KeyParameter instead of wrapping it in ParametersWithIV/AeadParameters.

Source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/crypto/modes/GcmBlockCipher.cs:123

                {
                    throw new ArgumentException("Invalid value for MAC size: " + macSizeBits);
                }

                macSize = macSizeBits / 8;
                keyParam = param.Key;
            }
            else if (parameters is ParametersWithIV)
            {
                ParametersWithIV param = (ParametersWithIV)parameters;

                newNonce = param.GetIV();
                initialAssociatedText = null;
                macSize = 16;
                keyParam = (KeyParameter)param.Parameters;
            }
            else
            {
                throw new ArgumentException("invalid parameters passed to GCM");
            }

            int bufLength = forEncryption ? BlockSize : (BlockSize + macSize);
            this.bufBlock = new byte[bufLength];

            if (newNonce == null || newNonce.Length < 1)
            {
                throw new ArgumentException("IV must be at least 1 byte");
            }

            if (forEncryption)
            {
                if (nonce != null && Arrays.AreEqual(nonce, newNonce))
                {
                    if (keyParam == null)
                    {
                        throw new ArgumentException("cannot reuse nonce for GCM encryption");
                    }

View on GitHub (pinned to 53fb989abc)

Solutions

1. Wrap the key: new ParametersWithIV(keyParameter, iv) or new AeadParameters(keyParameter, macSize, iv)
2. Ensure the IV is generated/passed at Init time (GCM is stateful and requires a fresh nonce per encryption)
3. Check for accidentally passing null or a KeyParameter directly to Init

When it happens

Trigger: Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/crypto/modes/GcmBlockCipher.cs:123 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/3f03305e868d166b. Report an issue: GitHub.