CVE-2026-84897
- Source
- https://cve.org/CVERecord?id=CVE-2026-84897
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-84897.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-84897
- Published
- 2026-10-07T02:42:28Z
- Modified
- 2026-10-09T07:06:05Z
- Severity
-
- 6.9 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/AU:Y CVSS Calculator
- Summary
- wolfSSH server accepts server-to-client DH group exchange messages from an unauthenticated client, causing pre-authentication primality-test CPU exhaustion and key exchange role confusion
- Details
-
src/internal.c in wolfSSL wolfSSH through 1.5.0 admits the server-to-client Diffie-Hellman group exchange messages SSH_MSG_KEX_DH_GEX_GROUP (31) and SSH_MSG_KEX_DH_GEX_REPLY (33) when a server receives them from an unauthenticated client. IsMessageAllowedServer() applies no direction check to the key exchange message range: when the peer is keying and no particular message is expected, which is the state a server is in for the whole window after it processes the client's KEXINIT because nothing sets handshake->expectMsgId there, the function falls out of its expectation branch without a verdict and reaches a numeric bound that admits every message id from 30 through 34. A client that negotiates diffie-hellman-group-exchange-sha256 and then sends message 31 makes the server run the client-side handler DoKexDhGexGroup(), which validates the attacker-supplied group with two 8-round Miller-Rabin primality tests, one on p and one on (p-1)/2, on a value of up to 8192 bits. The handler then returns success: the server stores the attacker's prime and generator, generates a Diffie-Hellman key pair in the attacker's group, and sends the client-role message SSH_MSG_KEX_DH_GEX_INIT (32) back to the attacker. Published RFC 3526 safe primes are the worst-case input and cost the attacker nothing to obtain. The primality validation was added in 1.5.0; versions from 1.2.0 through 1.4.22 admit the same message and enter the same client-role path without the primality cost. Message 33 is admitted as well, but on a server it is rejected before any cryptography because no public key check callback is registered, so it carries no comparable cost. Builds that define WOLFSSH_NO_DH_GEX_SHA256, which is implied by WOLFSSH_NO_DH or NO_SHA256, are unaffected.
- Database specific
{ "cna_assigner": "wolfSSL", "cwe_ids": [ "CWE-372", "CWE-400", "CWE-405" ], "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84897.json", "unresolved_ranges": [ { "extracted_events": [ { "introduced": "1.2.0" }, { "fixed": "1.6.0" } ], "source": "AFFECTED_FIELD" }, { "extracted_events": [ { "introduced": "30" }, { "fixed": "34" } ], "source": "DESCRIPTION" } ] }- References
-
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84897.json
- https://nvd.nist.gov/vuln/detail/CVE-2026-84897
- https://github.com/wolfSSL/wolfssh/commit/a472f1ee2b653f623d85ef2297321733f1dbfd22
- https://github.com/wolfSSL/wolfssh/pull/1221
- https://github.com/wolfSSL/wolfssh
- https://www.rfc-editor.org/rfc/rfc3526.html
- https://www.rfc-editor.org/rfc/rfc4419.html
Affected packages
Git / github.com/wolfssl/wolfssh
Affected ranges
- Type
- GIT
- Repo
- https://github.com/wolfssl/wolfssh
- Events
-
Introduced0 Unknown introduced commit / All previous commits are affectedFixedIntroducedFixedFixed
- Database specific
-
Show details
{ "extracted_events": [ { "introduced": "0" }, { "fixed": "1.5.0" }, { "introduced": "1.2.0" }, { "fixed": "1.4.22" } ], "source": [ "DESCRIPTION", "REFERENCES" ] }
Affected versions
v1.*
Database specific
source
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-84897.json"
vanir_signatures
[
{
"deprecated": false,
"digest": {
"function_hash": "332597429388241481065802417261341409358",
"length": 2367
},
"id": "CVE-2026-84897-00ddc3b5",
"signature_type": "Function",
"signature_version": "v1",
"source": "https://github.com/wolfssl/wolfssh/commit/a472f1ee2b653f623d85ef2297321733f1dbfd22",
"target": {
"file": "src/internal.c",
"function": "IsMessageAllowedServer"
}
},
{
"deprecated": false,
"digest": {
"function_hash": "128697116366816681178397962724568946588",
"length": 5650
},
"id": "CVE-2026-84897-474b24ff",
"signature_type": "Function",
"signature_version": "v1",
"source": "https://github.com/wolfssl/wolfssh/commit/a472f1ee2b653f623d85ef2297321733f1dbfd22",
"target": {
"file": "tests/regress.c",
"function": "main"
}
},
{
"deprecated": false,
"digest": {
"line_hashes": [
"118513238373630913010649926792335052979",
"249562867172711739799557390989647643018",
"325921520442702441106489839726675749863",
"76289822188778458399863853977056367152",
"52564300302719386044077990138923678774",
"321929433519072388629500615019388727461",
"94056652126704302590815800423611593456"
],
"threshold": 0.9
},
"id": "CVE-2026-84897-63bf690c",
"signature_type": "Line",
"signature_version": "v1",
"source": "https://github.com/wolfssl/wolfssh/commit/a472f1ee2b653f623d85ef2297321733f1dbfd22",
"target": {
"file": "tests/regress.c"
}
},
{
"deprecated": false,
"digest": {
"line_hashes": [
"185246754689052513008561199853287132380",
"137609406753648681267639826552501788982",
"149705089427072683951731583736537310304",
"150271123820429758589687398548444471965"
],
"threshold": 0.9
},
"id": "CVE-2026-84897-ea0e1f8e",
"signature_type": "Line",
"signature_version": "v1",
"source": "https://github.com/wolfssl/wolfssh/commit/a472f1ee2b653f623d85ef2297321733f1dbfd22",
"target": {
"file": "src/internal.c"
}
}
]
vanir_signatures_modified
"2026-10-09T07:06:05Z"