CriticalCVE-2026-34926

    Trend Micro Apex One (On-Premise) Directory Traversal Vulnerability (CVE-2026-34926)

    Published Last modified In CISA KEV since Sources: CVE.org, EUVD, BSI

    What is affected, what to do

    A directory traversal vulnerability in the Apex One (on-premise) server could allow a pre-authenticated local attacker to modify a key table on the server to inject malicious code to deploy to agents on affected installations. This vulnerability is only exploitable on the on-premise version of Apex One and a potential attacker must have access to the Apex One Server and already obtained administrative credentials to the server via some other method to exploit this vulnerability.

    The vulnerability is being actively exploited; treat it as a priority. Update Trend Micro TrendAI Apex One to version 14.0.0.17079, Trend Micro TrendAI Apex One as a Service to version 14.0.20731. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Trend Micro TrendAI Apex One lt 2019 (14.0)..14.0.0.17079
    • Trend Micro TrendAI Apex One as a Service lt SaaS..14.0.20731
    Fixed in
    • Trend Micro TrendAI Apex One 14.0.0.17079
    • Trend Micro TrendAI Apex One as a Service 14.0.20731

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    6.7

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    6.7

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: CVE.org, EUVD, BSI

    13.4 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 96.4

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    225.68 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.7 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    6.7
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    13.4 %
    Elevated — model estimates 10-50% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    96.4
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-23

    Response and mitigation

    Why act now?

    Prioritisation rationale

    On its own this is a moderate-severity bug with moderate exploitation likelihood, because it requires local access and administrative credentials already in hand. Its real value to attackers is post-exploitation. The changed scope lets anyone who owns the management server push code to every endpoint under the guise of a trusted security product, which turns a foothold into fleet-wide execution and explains its KEV listing. Trend Micro management servers have been targeted repeatedly in the past. Organisations running on-premise Apex One should treat patching as high priority within days, especially where server admin access is weakly controlled. SaaS customers only need to verify their version.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Patch now: Upgrade Apex One (on-premise) 2019 (14.0) to at least SP1 Build 17079 (14.0.0.17079). The context also lists SP1 CP Build 18012 as a threshold. Prefer the latest available Critical Patch, and confirm the exact build against the Trend Micro advisory.
      • Verify Apex One as a Service (SaaS): The vendor has updated to 14.0.20731. Confirm in the console that your tenant and agents report this version. No customer patching is required, but record the check.
      • Rotate admin credentials on the Apex One server: Exploitation requires admin credentials that an attacker has already obtained. Reset local administrator passwords, Apex One console accounts and server service accounts, then kill active sessions.
      • Compromise assessment: Review interactive and RDP logons to the Apex One server over the last 30–90 days. Diff the install directory (typically ...\Trend Micro\Apex One\PCCSRV\) against a known-good install or backup.
      • Freeze agent deployments: Hold manual deployments, component rollouts and policy pushes until server integrity is confirmed. If you suspect tampering, cut the server off from the agent network so it cannot distribute payloads.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Place the Apex One server in a dedicated management tier. Restrict RDP, SMB and the web console to PAWs or a jump host, and leave agent communication paths intact.
      • IAM / least privilege: Limit local admin on the server to a few named accounts. Enforce MFA on the console and the jump host, and eliminate shared accounts. Pin local Administrators membership via GPO Restricted Groups.
      • Server endpoint hardening: Apply SACL-based file integrity monitoring to the PCCSRV tree. Use AppLocker or WDAC to block unsigned binaries running from web and download paths. Remove unused roles and admin tooling such as PsExec.
      • Agent-side control: Monitor child processes of the Apex One agent with Sysmon or a secondary EDR on representative clients. This is your last line of defence if the server pushes malicious code.
      • Configuration baselining: Hash and store a baseline of the agent-deployment configuration files and tables after each update. Reconcile any drift against change tickets.

    3. Runbook step 3

      Detection rules

      • Windows Security log (server): Event ID 4624 (logon type 10/2) and 4672 outside maintenance windows or from unexpected source IPs. KQL: SecurityEvent | where Computer has "apexone" and EventID in (4624,4672) and LogonType in (2,10).
      • Sysmon EID 11 / Event ID 4663: Writes under PCCSRV by processes that are not Trend Micro services, such as cmd.exe, powershell.exe, or w3wp.exe with an unusual path. Sigma shape: TargetFilename|contains: '\PCCSRV\' AND NOT Image|contains: '\Trend Micro\'.
      • IIS / console logs: Requests to the Apex One web console with traversal sequences (../, ..%2f, %2e%2e, ..\) in the URI or parameters. SPL: index=iis host=apexone* (uri_query="*..%2f*" OR uri_query="*../*" OR uri_query="*%2e%2e*").
      • EDR process ancestry (agents): Apex One agent processes (e.g. PccNTMon.exe, TmListen.exe, NTRtScan.exe) spawning cmd.exe, powershell.exe, rundll32.exe or mshta.exe, or dropping executables outside the Trend Micro directory. Treat it as high-fidelity when the pattern appears on many hosts at once.
      • Network telemetry (Zeek/Suricata): Client beaconing to unfamiliar destinations shortly after an agent update cycle. Also watch for non-Trend-Micro-signed executables served from the Apex One server (files.log, MIME application/x-dosexec).

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A directory traversal vulnerability in the Apex One (on-premise) server could allow a pre-authenticated local attacker to modify a key table on the server to inject malicious code to deploy to agents on affected installations. This vulnerability is only exploitable on the on-premise version of Apex One and a potential attacker must have access to the Apex One Server and already obtained administrative credentials to the server via some other method to exploit this vulnerability.

    Source: cvelistv5, CISA KEV Catalog, NVD (NIST), ENISA EUVD, CVE.org (MITRE), BSI CSAF, BSI WID Portal

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    Trend Micro, Inc.TrendAI Apex One
    • 2019 (14.0) – < 14.0.0.17079
    • 14.0.0.17079
    Trend Micro, Inc.TrendAI Apex One as a Service
    • SaaS – < 14.0.20731
    • 14.0.20731
    trendmicroapex_one
    • < 14.0.0.17079
    • < 14.0.20731
    • 14.0.0.17079
    • 14.0.20731
    Trend MicroApex One
    • <SP1 Build 17079
    • <SP1 CP Build 18012
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-23Relative Path Traversal

      Base

      The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.

      Entry at MITRE CWE-23

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    PoC-in-GitHub (nomi-sec)CVE-2026-34926 (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    One NVD translation into another language is hidden.

    Linked advisories

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    Badge preview for CVE-2026-34926
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-34926"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-34926.svg?lang=en" alt="CVE-2026-34926 – NEOSEC Intel" height="20"></a>