CriticalCVE-2026-59310

    vCenter directory-traversal vulnerability (CVE-2026-59310)

    Published Last modified In CISA KEV since Sources: pwn.watch, CVE.org, Vmware Vmsa, SingCERT, BSI

    What is affected, what to do

    VMware vCenter contains a directory traversal vulnerability in the Syslog server. A malicious actor with network access to vCenter may exploit this issue to execute arbitrary code.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. Update VMware vCenter to version 9.1.0.0300, VMware vCenter to version 9.0.2.0100. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • VMware Cloud Foundation eq 9.1.x.x..9.1.x.x
    • VMware Cloud Foundation eq 9.0.x.x..9.0.x.x
    • VMware Cloud Foundation eq 5.x..5.x
    • VMware vSphere Foundation eq 9.1.x.x..9.1.x.x
    • VMware vSphere Foundation eq 9.0.x.x..9.0.x.x
    • VMware vCenter lt 9.1.x.x..9.1.0.0300
    • VMware vCenter lt 9.0.x.x..9.0.2.0100
    • VMware vCenter gte 8.0..*
    • VMware Telco Cloud Infrastructure eq 3.0..3.0
    • VMware Telco Cloud Platform eq 5.1.x..5.1.x
    • VMware Telco Cloud Platform eq 5.0.x..5.0.x
    • VMware Telco Cloud Platform eq 4.x..4.x
    • VMware Telco Cloud Platform eq 3.0..3.0
    Fixed in
    • VMware vCenter 9.1.0.0300
    • VMware vCenter 9.0.2.0100

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

    Metrics

    9.8

    Priority

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

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: pwn.watch, CVE.org, Vmware Vmsa, SingCERT, BSI

    2.6 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 85.0

    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
    253.86 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
    9.8 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
    9.8
    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“.

    Read in glossary
    2.6 %
    Moderate — model estimates 1-10% 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
    85.0
    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-22

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication or user interaction and leads straight to code execution on the control plane of the entire virtualisation estate — owning vCenter effectively means owning every managed ESXi host and VM. CISA flags known ransomware campaign use, and vCenter is a favoured target precisely because it lets an operator encrypt all workloads, often including backup systems, in a handful of steps. The modelled exploitation likelihood is only moderately elevated, but the KEV listing confirms real-world attacks, so that figure should not soften urgency. Treat it as an emergency change wherever the vCenter syslog ports are reachable from anything broader than the ESXi management network; in a strictly isolated management segment it remains critical with a patch window of a few days at most.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Apply the vendor fix: Patch available from the vendor — look up the fixed version in the Broadcom/VMware Security Advisory (VMSA) for CVE-2026-59310. Inventory every vCenter Server instance (8.0 in particular) and patch on an emergency change. Take a snapshot or file-based backup via VAMI (port 5480) first.
      • Restrict network reachability now: Firewall the vCenter Server Appliance syslog receiver ports (typically 514/udp, 514/tcp, 1514/tcp for TLS — verify against your configuration) so only the ESXi hosts that actually send logs can reach them. Kill any exposure from the internet, user networks or DMZ segments.
      • Compromise assessment around the patch: Exploitation yields code execution on the appliance, so patching alone does not evict an intruder. Hunt for unknown files in web and config directories, new cron entries, modified authorized_keys and unexpected local accounts before and after patching (see Detection rules).
      • Rotate privileged credentials if anything looks off: administrator@vsphere.local, appliance root, service accounts holding vCenter roles, and root on managed ESXi hosts (vCenter controls them via vpxuser).
      • Ransomware readiness: Verify offline/immutable backups of VMs and the vCenter configuration; check whether backup infrastructure is reachable with vCenter credentials and temporarily decouple it if so.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Keep vCenter and ESXi management in a dedicated management VLAN, reachable only from hardened admin jump hosts (PAWs) with MFA. Allow the appliance's syslog ports from ESXi host addresses only; drop and log everything else.
      • Syslog architecture: If vCenter does not need to be a syslog destination, repoint ESXi hosts to a separate hardened collector or directly to the SIEM and disable or locally firewall the syslog listener on the appliance.
      • IPS/NIDS signature: Suricata/Snort rule on syslog traffic towards vCenter flagging traversal sequences in the message header (hostname/tag field), e.g. alert udp any any -> $VCENTER 514 (msg:"Possible vCenter syslog path traversal"; content:"../"; sid:...;), mirrored for TCP 514/1514 and URL-encoded variants (%2e%2e%2f).
      • Appliance and host hardening: Disable SSH and the BASH shell on the VCSA unless operationally required, enabling them only time-boxed. Enable Lockdown Mode and disable SSH on ESXi hosts to slow lateral movement and mass encryption.
      • IAM/least privilege: Review vCenter SSO roles, remove stale administrators, scope AD integration to dedicated admin groups, and never map Domain Admins to vCenter Administrator.

    3. Runbook step 3

      Detection rules

      • Network telemetry (Zeek/Suricata): Look in Zeek syslog.log for messages to vCenter whose hostname or program field contains ../, ..\ or encoded variants, and for syslog senders that are not known ESXi hosts. Example SPL: index=zeek sourcetype=zeek_syslog dest_ip=<vcenter> (message="*../*" OR message="*%2e%2e*").
      • File integrity (auditd on the VCSA): Watch /etc/cron.d, /etc/crontab, /root/.ssh/authorized_keys, /etc/rc.d and the vSphere service web directories; alert when rsyslogd writes anywhere outside /var/log. Example: -w /etc/cron.d -p wa -k vc_persist, then filter on exe="/usr/sbin/rsyslogd" with paths outside /var/log.
      • Process ancestry: Child processes of rsyslogd, vpxd or the vSphere Java services such as sh, bash, python, curl, wget or nc are highly suspicious. Sigma shape: ParentImage|endswith: ['/rsyslogd','/java','/vpxd'] and Image|endswith: ['/bash','/sh','/curl','/wget','/python3'].
      • vCenter events (follow-on activity): In vCenter events or the SIEM, hunt for new SSO users, role/permission changes, SSH being enabled on ESXi hosts, bulk VM power-offs, snapshot deletions and registration of unknown VMs — classic precursors to hypervisor-level encryption.
      • Outbound connections: The appliance normally talks only to known peers (ESXi, AD, NTP, DNS, update repository). Treat new outbound sessions to external IPs, especially on unusual ports, as possible reverse shells or exfiltration.

    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

    VMware vCenter contains a directory traversal vulnerability in the Syslog server. A malicious actor with network access to vCenter may exploit this issue to execute arbitrary code.

    Source: pwn.watch, cvelistv5, CISA KEV Catalog, NVD (NIST), CVE.org (MITRE), vmware_vmsa, CSA/SingCERT, 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
    VMwareCloud Foundation
    • 9.0.x.x
    • 5.x
    • 9.1.x.x
    • —
    • —
    • —
    VMwareTelco Cloud Infrastructure
    • 3.0
    • —
    VMwareTelco Cloud Platform
    • 4.x
    • 3.0
    • 5.1.x
    • 5.0.x
    • —
    • —
    • —
    • —
    VMwarevCenter
    • 9.1.x.x – < 9.1.0.0300
    • 9.0.x.x – < 9.0.2.0100
    • ≥ 8.0
    • 9.1.0.0300
    • 9.0.2.0100
    • —
    VMwarevSphere Foundation
    • 9.0.x.x
    • 9.1.x.x
    • —
    • —
    vmwarevcenter_server
    • 8.0
    • 9.0 – < 9.0.2.0100
    • < 8.0
    • 9.1 – < 9.1.0.0300
    • —
    • 9.0.2.0100
    • 8.0
    • 9.1.0.0300

    Vendors and products

    Weakness classes (CWE)

    • CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

      Base

      The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

      Entry at MITRE CWE-22

    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)vc-strike (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2026-59310 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2026-59310-POC (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2026-59310 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2026-59310 (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • support.broadcom.comBroadcom VMware vCenter — CVE-2026-59310pwn-watch
    • medium.com@quirso_de/global-exploitation-of-cve-2026-59310-by-suspected-c…Third-party advisory
    • medium.com@quirso_de/active-exploitation-of-cve-2026-59310-361-victim-ips…Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-59310government-resource
    • pwn.watchpwn.watch: Broadcom VMware vCenter: Broadcom VMware vCenter Path Traversal Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2026-59310pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

    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).

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentchanged
      {"id":"CVE-2026-59310","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-18T17:44:09.652188Z"}
      {"id":"CVE-2026-59310","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-07-29T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Linked advisories

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2026-59310
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-59310"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-59310.svg?lang=en" alt="CVE-2026-59310 – NEOSEC Intel" height="20"></a>