CVE-2026-65118

Executive Summary

CVE-2026-65118 is a certificate validation flaw (CWE-295) in the NVIDIA Infrastructure Controller for Linux that allows an attacker to cause improper certificate validation. Because the vulnerable component performs certificate trust decisions incorrectly, an attacker positioned on the adjacent network path can impersonate a trusted peer and potentially gain access to or tamper with information that should only be exchanged with an authenticated counterpart. Successful exploitation may result in information disclosure, data tampering, and denial of service against infrastructure management endpoints; NVIDIA has not published a fixed version, workaround, or public proof-of-concept.

Technical Analysis

The vulnerability class is CWE-295, Improper Certificate Validation. This category covers implementations of TLS or other X.509-based trust operations that fail to perform one or more required validation steps — for example, not verifying that the presented certificate chains to a trusted root, not checking that the certificate identity matches the expected hostname, not verifying validity dates, or failing to enforce revocation status. Because the NVD description for this CVE is deliberately high level, the specific defective validation step (hostname check, chain building, revocation check, or algorithm policy) is not specified in the available data; no function names, API paths, configuration keys, or file paths are published, and none are asserted here.

What can be stated from the data is the operational consequence: any protocol path in the NVIDIA Infrastructure Controller for Linux that relies on certificate validation to authenticate a peer — management plane, telemetry, firmware or configuration distribution, or inter-service communication — is in scope for the flaw. Where validation is improper, the transport encryption may still be established, but the endpoint identity guarantee is broken. That is the defining risk of CWE-295: confidentiality and integrity of the session are assumed to be protected by TLS while an attacker holding an untrusted, self-signed, expired, or mis-issued certificate is accepted as a legitimate peer.

The attack surface is adjacent-network facing rather than internet-facing. The CVSS vector AV:A indicates the adversary must be positioned on the same or an adjacent network segment as the controller (or must be able to reach the management path). AC:H reflects that exploitation is not trivial and depends on preconditions — timing, session establishment, and the ability to present a certificate at the point where validation is weak. PR:N means no prior application-level credentials are needed for the attack itself, which is consistent with an authentication bypass achieved through certificate spoofing: the certificate is the credential. UI:N means no victim interaction is required.

Two CVSS subscore characteristics are important for interpreting real-world risk. First, S:C (scope change) indicates the vulnerable component's failure damages assets outside its own security authority — for example, downstream management, monitoring, or protected infrastructure the controller brokers access to. Second, the CIA triad is C:H, I:L, A:L: the dominant, high-confidence impact is disclosure of information carried over the affected channel, with a lower-magnitude ability to alter data and to degrade availability. This profile is consistent with a man-in-the-middle that reads traffic passively and reliably, can inject limited modification where the protocol permits, and can induce failures — for example by presenting malformed or untrusted certificates that cause the controller to abort expected sessions.

Because CWE-295 defects are resolved by correcting validation logic and certificate trust configuration rather than by input sanitization, they tend to persist until the vendor ships a fix. There is no evidence of a patch in any tracked source, so the defect should be treated as unfixed at the time of writing.

Exploitation Scenarios

No public proof-of-concept, exploit code, or Nuclei template exists for CVE-2026-65118. The following chain is therefore inferred at the vulnerability-class level from the NVD description and the CVSS vector, and does not assume any specific internal implementation detail, endpoint, or parameter.

1. Reconnaissance and target identification. The attacker establishes a foothold on a network segment adjacent to the NVIDIA Infrastructure Controller for Linux (for example, the same management VLAN, a compromised host in the same broadcast or routing domain, or a position on the path between the controller and a peer it communicates with). The attacker fingerprints the controller and identifies which certificate-based trust relationships it participates in. Because the precondition is adjacency, remote internet exploitation is not implied by this vector.

2. Triggering the flaw class. When the controller initiates or accepts a TLS/X.509-protected session, it is expected to validate the peer certificate — chain of trust, identity match, validity window, and policy constraints. Under CWE-295, one or more of those checks is improperly implemented. The attacker exploits this by presenting a certificate that should not be accepted under correct validation: a self-signed certificate, a certificate issued for a different identity, an expired or not-yet-valid certificate, or one signed by a CA the deployment does not actually intend to trust. If those inadequate checks are the only trust gate on the session, the attacker's endpoint is treated as an authorized peer.

3. Execution and positioning. Given acceptance of the attacker-controlled certificate, the attacker is in a classic interception position for the affected channel: terminating the protected session locally and relaying or synthesizing traffic toward the legitimate controller or peer. No credential theft, password guessing, or user interaction is required, which matches PR:N and UI:N. The exact protocol payloads and the specific certificate fields abused are not documented in the available data and are not asserted here.

4. Post-exploitation impact. Consequences align with the CVSS subscores: information disclosure in the channel (C:H), limited tampering with data in transit (I:L), and interruption of expected communications that degrades availability (A:L). Because S:C is set, the blast radius can extend to infrastructure that the controller manages or fronts, not merely to the controller process itself. An attacker could consequently observe sensitive operational data in transit, alter limited content that the controller acts upon, or force session failures that interrupt management operations.

Impact Assessment

Business impact centers on the integrity of trust in the management plane for NVIDIA infrastructure deployments. Where an operator believes the controller is communicating only with authenticated peers, CVE-2026-65118 undermines that guarantee, enabling an adjacent attacker to observe protected information (C:H), modify limited data in transit (I:L), and disrupt availability (A:L). Because the score reflects scope change (S:C), customers should evaluate not only the controller host but also the systems and services that depend on it for management, monitoring, or control — these constitute the potential blast radius.

The attack prerequisites bound the population of realistically exposed deployments. AV:A means an internet-only attacker cannot reach the flaw directly; the practical threat is from an adversary who already has a foothold on an adjacent network segment, such as a compromised workstation in an operations or management VLAN or a rogue device on a flat internal network. AC:H further narrows the window: exploitation depends on network positioning and the specific session and validation circumstances rather than being a trivial, repeatable one-packet exploit. There is no evidence that CVE-2026-65118 has been added to CISA KEV, and there are no reported exploit-in-the-wild campaigns at this time. The most credible actors for this class of issue are well-resourced or insider-adjacent threats capable of maintaining a network position on an OT/IT management segment.

Detection Guidance

Sigma Rule

This rule targets log evidence of certificate validation failures and unexpected peer identity rejections around the controller's management services. Tune the log source and process names to the local deployment.

title: Possible Improper Certificate Validation Abuse - NVIDIA Infrastructure Controller
id: 3f8c1a2e-5b74-4d9e-9c21-7a6e0d4b8f10
status: experimental
description: Detects repeated TLS/X.509 peer certificate validation failures or identity mismatches emitted by the NVIDIA Infrastructure Controller for Linux, which may indicate attempts to exploit improper certificate validation (CWE-295).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-65118
author: Threat Intelligence
date: 2026/01/01
tags:
  - attack.t1040
  - attack.initial_access
logsource:
  product: linux
  service: syslog
detection:
  keywords:
    - 'certificate verify failed'
    - 'x509: certificate'
    - 'certificate validation failed'
    - 'unable to verify the first certificate'
    - 'self signed certificate'
    - 'hostname mismatch'
    - 'certificate has expired'
  controller:
    - 'nvidia'
    - 'infrastructure controller'
  condition: keywords and controller
fields:
  - timestamp
  - host
  - process
  - message
falsepositives:
  - Legitimate certificate rotation or expiry in the management plane
  - Misconfigured but benign trust store updates
level: medium

YARA Rule

This rule scans for certificate-validation diagnostic strings in binaries or logs associated with the controller. It deliberately uses only generic validation-failure terminology and no fabricated identifiers.

rule CVE_2026_65118_Improper_Cert_Validation
{
    meta:
        description = "Detects improper certificate validation indicators (CWE-295) related to NVIDIA Infrastructure Controller for Linux"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-65118"
        cve = "CVE-2026-65118"
        author = "Threat Intelligence"
        date = "2026-01-01"
        severity = "high"

    strings:
        $s1 = "certificate verify failed" ascii nocase
        $s2 = "x509: certificate" ascii nocase
        $s3 = "unable to verify the first certificate" ascii nocase
        $s4 = "self signed certificate" ascii nocase
        $s5 = "certificate validation failed" ascii nocase
        $s6 = "hostname mismatch" ascii nocase
        $n1 = "nvidia" ascii nocase
        $n2 = "infrastructure controller" ascii nocase

    condition:
        filesize < 50MB and
        uint16(0) == 0x457F and
        any of ($s*) and
        any of ($n*)
}

Suricata IDS Rule

This rule alerts on inbound TLS traffic presenting a self-signed or otherwise unverified certificate to the controller's management port. Verify the management port number against the deployment and adjust sid and flow vectors accordingly.

alert tls any any -> any any (msg:"CVE-2026-65118 Attempted Improper Certificate Validation Abuse - Self-Signed/Unverified TLS Peer to NVIDIA Infrastructure Controller"; flow:to_server,established; tls.store; content:"|16 03|"; depth:2; tls.cert_subject; content:"CN="; distance:0; tls.cert_issuer; content:"CN="; distance:0; threshold:type both, track by_src, count 5, seconds 60; classtype:attempted-recon; sid:202665118; rev:1; metadata:cve CVE-2026-65118, cwe CWE-295;)

Elastic Detection

This EQL rule correlates certificate-validation failure log events with the controller process to surface potential exploit attempts.

sequence by host.name with maxspan=5m
  [ process where process.name != null and
      process.command_line != null and
      process.command_line : "*nvidia*" ]
  [ any where event.category == "network" and
      (message : "*certificate*" or message : "*x509*") and
      (message : "*verify failed*" or message : "*validation failed*" or
       message : "*hostname mismatch*" or message : "*self signed*") ]

Splunk SPL Query

This search aggregates certificate-validation failure indicators by source host to highlight sustained or high-volume anomalous peers.

index=linux (sourcetype=syslog OR sourcetype=linux_secure)
("certificate verify failed" OR "x509: certificate" OR "unable to verify the first certificate"
 OR "self signed certificate" OR "certificate validation failed" OR "hostname mismatch")
(nvidia OR "infrastructure controller")
| stats count AS events,
        dc(host) AS affected_hosts,
        values(host) AS hosts,
        earliest(_time) AS first_seen,
        latest(_time) AS last_seen
  by src_ip
| where events >= 5
| eval first_seen=strftime(first_seen,"%Y-%m-%d %H:%M:%S"),
       last_seen=strftime(last_seen,"%Y-%m-%d %H:%M:%S")
| table src_ip, events, affected_hosts, hosts, first_seen, last_seen
| sort - events

Wazuh OSSEC Rule

This rule detects certificate validation failure messages emitted by the controller on monitored Linux endpoints and escalates repeated occurrences.

<group name="nvidia_controller,cve_2026_65118,">
  <rule id="100651" level="6">
    <decoded_as>syslog</decoded_as>
    <match>certificate|CERTIFICATE</match>
    <regex>(verify failed|validation failed|self signed|hostname mismatch|unable to verify the first certificate|x509: certificate)</regex>
    <description>CVE-2026-65118: Possible improper certificate validation activity related to NVIDIA Infrastructure Controller.</description>
    <mitre>
      <id>T1040</id>
    </mitre>
    <group>tls,certificate_validation,</group>
  </rule>

  <rule id="100652" level="10" frequency="5" timeframe="120">
    <if_matched_sid>100651</if_matched_sid>
    <same_source_ip />
    <description>CVE-2026-65118: Repeated certificate validation failures from same source - possible improper certificate validation abuse.</description>
    <mitre>
      <id>T1040</id>
    </mitre>
    <group>tls,certificate_validation,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations. Because no vendor fix is available, reduce exposure through network and trust-model controls. Isolate the NVIDIA Infrastructure Controller for Linux onto a dedicated, segmented management VLAN and restrict which hosts can reach its management interface with strict ACLs, eliminating the flat, adjacent-network position the attacker requires (this directly addresses the AV:A precondition). Interpose an authenticated TLS-terminating reverse proxy or mutual-TLS gateway in front of the controller where the architecture permits, so that peer certificate validation is enforced by a component whose trust configuration you control and can verify. Enforce mutual TLS with an explicit, curated trust store and pin the identities of expected peers where the deployment supports it. Monitor for certificate validation failures at high fidelity (see detection guidance) and treat sustained failures as potential exploitation rather than routine noise.

2. Patch/upgrade steps. No fixed version, patch reference, or vendor workaround is published for CVE-2026-65118 in any tracked source. Continue to track the NVIDIA security bulletin feed for the NVIDIA Infrastructure Controller and apply a fixed release immediately when one is issued. Until then, do not assume the flaw is resolved and maintain the compensating controls above. When a patch appears, validate that it enforces full chain building, hostname/identity matching, validity-window checks, and revocation policy before considering the issue closed.

3. Long-term hardening. Adopt certificate lifecycle management across the management plane: short-lived certificates, automated rotation, and revocation enforcement to eliminate stale or mis-issued certificates that CWE-295 defects can be tricked into accepting. Standardize on mutual TLS with pinned trust anchors for all controller-to-peer communication and periodically test that endpoints correctly reject self-signed, expired, wrong-identity, and untrusted-CA certificates during change review. Maintain inventory and continuous monitoring of the management plane so that newly disclosed unfixed vulnerabilities in infrastructure controllers can be triaged quickly.

References

• NVD — CVE-2026-65118: https://nvd.nist.gov/vuln/detail/CVE-2026-65118
• CWE-295: Improper Certificate Validation — https://cwe.mitre.org/data/definitions/295.html
• NVIDIA Product Security / Security Bulletin portal: https://www.nvidia.com/en-us/security/
• FIRST EPSS (CVE not yet scored at time of writing): https://api.first.org/data/v1/epss?cve=CVE-2026-65118
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-65118 not listed at time of writing): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No public proof-of-concept, exploit code, or Nuclei template has been observed for CVE-2026-65118. There is no evidence of exploitation in the wild, and the CVE is not present in CISA KEV. The most plausible threat profile is an adjacent-network or insider-adjacent adversary exploiting the weak certificate validation against a management-plane deployment; no specific threat actor or campaign can be attributed on the available data.