CVE-2026-64389
Is CVE-2026-64389 real, exploitable, or a false positive? Here's the community verdict.
signals
public sources
High CVSS base score, but low real-world exploitation probability (EPSS). Likely less urgent than the score implies.
baseline read
auto · not a community verdict
Real, but low real-world risk
A genuine vulnerability on paper, but EPSS shows little real-world exploitation — the base score may overstate urgency. This is not the same as a false positive.
Based on CVSS · FIRST EPSS
Confirm or dispute →CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate NTLMv2 response before updating session key ksmbd_auth_ntlmv2() derives the NTLMv2 session key into sess->sess_key before it verifies the NTLMv2 response. ksmbd_decode_ntlmssp_auth_blob() then continues into KEY_XCH even when ksmbd_auth_ntlmv2() failed. With SMB3 multichannel binding, the failed authentication operates on an existing session and the session setup error path does not expire binding sessions. A client can send a binding session setup with a bad NT proof and KEY_XCH and still modify sess->sess_key before STATUS_LOGON_FAILURE is returned. Relevant path: smb2_sess_setup() -> conn->binding = true -> ntlm_authenticate() -> session_user() -> ksmbd_decode_ntlmssp_auth_blob() -> ksmbd_auth_ntlmv2() -> calc_ntlmv2_hash() -> hmac_md5_usingrawkey(..., sess->sess_key) -> crypto_memneq() returns mismatch -> KEY_XCH arc4_crypt(..., sess->sess_key, ...) -> out_err without expiring the binding session Derive the base session key into a local buffer and copy it to sess->sess_key only after the proof matches. Return immediately on authentication failure so KEY_XCH is only processed after successful authentication.
References
Published
Embed this verdict
[](https://www.truepositive.app/cve/CVE-2026-64389)<a href="https://www.truepositive.app/cve/CVE-2026-64389"><img src="https://www.truepositive.app/cve/CVE-2026-64389/badge.svg" alt="TruePositive verdict for CVE-2026-64389"></a>Live badge that updates automatically as the community verdict changes.
Community ground truth
Be the first practitioner to weigh in
So far this is only TruePositive's editorial baseline from public sources. Add your real-world verdict below — it becomes the signal the next person triaging this relies on.
🥇 The first 50 practitioners to contribute earn a Founding Contributor badge.
In your experience, is this finding real and exploitable?
awaiting field verdictsCurated baseline: A curated baseline from public sources, shown separately from community verdicts.
No account needed. Anonymous verdicts post as an unverified signal. Log in to make yours verified and earn reputation.
Field notes & remediation
Verdicts are the quick signal. Notes are the evidence and fixes behind them.
- 0
This scores high on paper (CVSS 8.2) but the real-world signal is low. It is not in CISA KEV and no public exploit was found, and near-term exploitation looks unlikely (EPSS about 0%). Verify your own exposure before treating it as urgent. It is reachable over the network with no authentication and no user interaction, which is the most dangerous profile. Not an emergency for most teams, but patch it in your normal cycle and check whether the affected component is actually exposed in your setup.