ASA-SEC-024HighCisco ASA

Weak IPsec transform set or proposal

Base severity

High

Area

IPSec VPN

Platform

Cisco ASA

Evidence level

Fact1.00

Benchmark reference

Reads the export, not the device

ConfigProof reads a configuration export. This control is evaluated against the objects in that file, and it reports what the file says. It does not connect to the device and sees no traffic, so a finding here describes the configuration, not what the firewall is doing right now.

Why it matters

DES, 3DES, NULL encryption and MD5 integrity protect the tunnel's traffic with cryptography that is broken or none at all.

How to fix it

Web interface

The steps below are written for the web interface. A finding raised on your own export carries the same steps with your object names filled in.

In ASDM: Configuration > Site-to-Site VPN > Advanced > IPsec Proposals (Transform Sets), edit the proposal to AES-GCM-256 or AES-256 with SHA-256, and point the crypto maps at it. Apply and save.
On the CLI: crypto ipsec ikev2 ipsec-proposal <name>, protocol esp encryption aes-gcm-256, protocol esp integrity null, then crypto map <map> <seq> set ikev2 ipsec-proposal <name>, and write memory.

Cisco ASA CLI

configure terminalcrypto ipsec ikev2 ipsec-proposal <ipsec-proposal>protocol esp encryption aes-gcm-256protocol esp integrity nullexitcrypto map <crypto-map> <sequence> set ikev2 ipsec-proposal <ipsec-proposal>endwrite memory

An example. Values in angle brackets are yours to supply; a finding on your own export fills in the names it read. Typed in configuration mode; write memory saves it, with no separate commit. Read every line first.

Read it back

show crypto ipsec sa

Values to fill in3

<ipsec-proposal>: A name for the new IPsec proposal
<crypto-map>: The crypto map
<sequence>: The crypto map entry's sequence number

Before you type it3

Written from the ASA 9.x command reference and not run on a device: read each line before you paste it.
In multiple context mode, type it in the context it applies to (changeto context <name>).
The far end has to offer the same proposal, so coordinate the change with whoever runs it.

How to confirm the fix

Run show crypto ipsec sa and confirm the new transforms.

Limits

Both peers must agree before the old proposal is removed.

Compliance references

No benchmark recommendation is mapped to this control in this version.

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