doc: deprecate modp1, modp2, and modp5 groups

These MODP groups should not be used by new applications, and existing
applications should attempt to migrate to stronger groups (or different
key exchange mechanisms).

Some applications still rely on these particular groups, so Node.js will
likely maintain support, directly or indirectly, for the foreseeable
future.

Refs: #44539

doc/api/crypto.md

@@ -1185,15 +1185,20 @@ const dh = createDiffieHellmanGroup('modp16');
 
 The following groups are supported:
 
-* `'modp1'` (768 bits, [RFC 2409][] Section 6.1)
-* `'modp2'` (1024 bits, [RFC 2409][] Section 6.2)
-* `'modp5'` (1536 bits, [RFC 3526][] Section 2)
 * `'modp14'` (2048 bits, [RFC 3526][] Section 3)
 * `'modp15'` (3072 bits, [RFC 3526][] Section 4)
 * `'modp16'` (4096 bits, [RFC 3526][] Section 5)
 * `'modp17'` (6144 bits, [RFC 3526][] Section 6)
 * `'modp18'` (8192 bits, [RFC 3526][] Section 7)
 
+The following groups are still supported but deprecated (see [Caveats][]):
+
+* `'modp1'` (768 bits, [RFC 2409][] Section 6.1) <span class="deprecated-inline"></span>
+* `'modp2'` (1024 bits, [RFC 2409][] Section 6.2) <span class="deprecated-inline"></span>
+* `'modp5'` (1536 bits, [RFC 3526][] Section 2) <span class="deprecated-inline"></span>
+
+These deprecated groups might be removed in future versions of Node.js.
+
 ## Class: `ECDH`
 
 <!-- YAML

doc/api/deprecations.md

@@ -3197,9 +3197,28 @@ Type: Documentation-only
 
 The [`--trace-atomics-wait`][] flag is deprecated.
 
+### DEP0166: Weak `DiffieHellmanGroup` instances (`modp1`, `modp2`, `modp5`)
+
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/44588
+    description: Documentation-only deprecation.
+-->
+
+Type: Documentation-only
+
+The well-known MODP groups `modp1`, `modp2`, and `modp5` are deprecated because
+they are not considered secure against practical attacks. See
+[RFC 8247 Section 2.4][] for details.
+
+These groups might be removed in future versions of Node.js. Applications that
+rely on these groups should evaluate using stronger MODP groups instead.
+
 [Legacy URL API]: url.md#legacy-url-api
 [NIST SP 800-38D]: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
 [RFC 6066]: https://tools.ietf.org/html/rfc6066#section-3
+[RFC 8247 Section 2.4]: https://www.rfc-editor.org/rfc/rfc8247#section-2.4
 [WHATWG URL API]: url.md#the-whatwg-url-api
 [`"exports"` or `"main"` entry]: packages.md#main-entry-point-export
 [`--pending-deprecation`]: cli.md#--pending-deprecation

doc/api_assets/style.css

@@ -598,7 +598,8 @@ hr {
   padding-left: 5rem;
 }
 
-#toc .stability_0::after {
+#toc .stability_0::after,
+.deprecated-inline::after {
   background-color: var(--red2);
   color: var(--white);
   content: "deprecated";