EUVD-2026-62705
GHSA-9gg7-6hv8-w46w
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N
MITM/on-path position needed to impersonate the policy server, so AC:H; no auth (PR:N); scope change and traffic tampering give S:C/I:H with limited read (C:L) and no availability impact.
Primary rating from Vendor (ibm).
CVSS VectorVendor: ibm
Lifecycle Timeline
2DescriptionCVE.org
IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a remote attacker to impersonate the TNC policy server and modify traffic due to improper certificate validation.
AnalysisAI
TNC policy server impersonation in IBM AIX 7.2/7.3 and IBM PowerVM VIOS 4.1 lets a network-positioned attacker forge the Trusted Network Connect policy server and tamper with the traffic between it and the endpoint, because the client fails to properly validate the server's certificate (CWE-295). An attacker who can intercept the session can present a fraudulent certificate, read limited data and alter integrity-critical policy exchanges. IBM has released a fix; no public exploit identified at time of analysis, and the issue is not listed in CISA KEV.
Technical ContextAI
The affected component is the Trusted Network Connect (TNC) client stack shipped with IBM AIX and the PowerVM Virtual I/O Server (VIOS). TNC is the Trusted Computing Group's network access control architecture in which an endpoint's integrity posture is checked against a policy server before network access is granted; the trust of that exchange rests entirely on authenticating the policy server via its X.509 certificate. CWE-295 (Improper Certificate Validation) means the client does not correctly verify that certificate - e.g. failing to check the trust chain, hostname, or signature - so any party able to answer for the policy server is accepted. The CPEs cpe:2.3:a:ibm:aix and cpe:2.3:a:ibm:powervm_vios confirm both the base OS and the virtualization I/O server are affected, indicating shared TNC code across IBM Power platforms.
RemediationAI
Apply the IBM-provided fix per the vendor advisory at https://www.ibm.com/support/pages/node/7283858 (patch available per vendor advisory); consult that page for the specific AIX 7.2/7.3 and VIOS 4.1 APAR or ifix levels, as exact patched version strings were not included in the input data. Where the fix cannot be applied immediately and TNC is in use, reduce exposure by restricting the network paths between AIX/VIOS endpoints and the TNC policy server to trusted, segmented management VLANs so an attacker cannot obtain an on-path position, and pin or tightly control the policy server's certificate/trust store; if TNC-based access control is not required in a given environment, disabling it removes the attack surface at the cost of losing endpoint posture enforcement. Each of these is a compensating control only - segmentation does not fix the validation flaw, and disabling TNC forfeits its access-control function - so the vendor patch remains the durable remediation.
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Same weakness CWE-295 – Improper Certificate Validation
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External POC / Exploit Code
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