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From: https://github.com/jtesta/ssh-audit/pull/377
commit fcfe99834ade7a87fe5436c11284051734efabb5
Author: ranas-mukminov <ranas@run-as-daemon.dev>
Date: Fri, 2 Oct 2026 09:35:03 +0000
Subject: [PATCH] fix: treat Dropbear kexguess2 as negotiation marker, not
PQ-unsafe KEX
kexguess2@matt.ucc.asn.au is a Dropbear KEX guessing marker (data field
NULL), not an actual key-exchange algorithm. Flagging it with
WARN_NOT_PQ_SAFE is misleading (#375). Classify it like ext-info /
kex-strict pseudo-algorithms with an INFO note instead.
--- a/src/ssh_audit/ssh2_kexdb.py
+++ b/src/ssh_audit/ssh2_kexdb.py
@@ -80,6 +80,7 @@ class SSH2_KexDB: # pylint: disable=too-few-public-methods
INFO_WITHDRAWN_PQ_ALG = 'the sntrup4591761 algorithm was withdrawn, as it may not provide strong post-quantum security'
INFO_EXTENSION_NEGOTIATION = 'pseudo-algorithm that denotes the peer supports RFC8308 extensions'
INFO_STRICT_KEX = 'pseudo-algorithm that denotes the peer supports a stricter key exchange method as a counter-measure to the Terrapin attack (CVE-2023-48795)'
+ INFO_KEXGUESS2 = 'pseudo-algorithm / negotiation marker used by Dropbear to accelerate KEX guessing; not an actual key exchange'
# NIST PQC security levels: https://blog.cloudflare.com/pq-2025/
INFO_NIST_PQC_LEVEL_2 = 'rated at NIST PQC level 2 (at least as hard to break as SHA256)'
@@ -196,7 +197,7 @@ class SSH2_KexDB: # pylint: disable=too-few-public-methods
'kexAlgoECDH256': [[], [FAIL_NSA_BACKDOORED_CURVE], [WARN_NOT_PQ_SAFE]],
'kexAlgoECDH384': [[], [FAIL_NSA_BACKDOORED_CURVE], [WARN_NOT_PQ_SAFE]],
'kexAlgoECDH521': [[], [FAIL_NSA_BACKDOORED_CURVE], [WARN_NOT_PQ_SAFE]],
- 'kexguess2@matt.ucc.asn.au': [['d2013.57'], [], [WARN_NOT_PQ_SAFE]],
+ 'kexguess2@matt.ucc.asn.au': [['d2013.57'], [], [], [INFO_KEXGUESS2]], # Dropbear KEX guessing marker (not a real algorithm).
'm383-sha384@libassh.org': [[], [FAIL_UNPROVEN], [WARN_NOT_PQ_SAFE]],
'm511-sha512@libassh.org': [[], [FAIL_UNPROVEN], [WARN_NOT_PQ_SAFE]],
'mlkem768x25519-sha256': [['9.9'], [], [], [INFO_DEFAULT_OPENSSH_KEX_100, INFO_HYBRID_PQ_X25519_KEX]],
--- a/test/test_ssh2_kexdb.py
+++ b/test/test_ssh2_kexdb.py
@@ -48,6 +48,7 @@ def test_kex_pq_unsafe(self):
"ext-info-s",
"kex-strict-c-v00@openssh.com",
"kex-strict-s-v00@openssh.com",
+ "kexguess2@matt.ucc.asn.au", # Dropbear negotiation marker, not a KEX algorithm
"mlkem768x25519-sha256",
"sntrup4591761x25519-sha512@tinyssh.org",
"sntrup761x25519-sha512@openssh.com",
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