CriticalCVE-2026-72529

    TrueConf Server Missing Authentication for Critical Function Vulnerability (CVE-2026-72529)

    Published Last modified In CISA KEV since Sources: pwn.watch, CVE.org

    What is affected, what to do

    A remote unauthorized attacker with network access via port 4307/TCP to the TrueConf server versions 5.3.X to 5.3.9, 5.4.X to 5.4.9, 5.5.X to 5.5.5, and earlier could execute an arbitrary script by calling an undocumented function.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Conflicting version data — version display is hidden until the data is resolved.

    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: Vendor (CNA), CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: pwn.watch, CVE.org

    1.5 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 73.5

    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
    216.09 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
    CVSS v4

    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
    9.3
    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
    1.5 %
    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
    73.5
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    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-306

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable with no authentication and no user interaction, and it gives an attacker arbitrary script execution on the server — full loss of confidentiality, integrity and availability for the conferencing platform. The model-based exploitation likelihood is only moderate and CISA reports no known ransomware use. KEV listing nonetheless confirms real-world attacks, typically against self-hosted video-conferencing infrastructure in government, industrial and critical-infrastructure-adjacent organisations, where the server makes a convenient foothold into internal networks. If 4307/TCP is reachable from the internet, treat this as critical with a 24 h remediation target; for internal-only, segmented instances, handle it as high priority within your emergency patch cycle.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory affected servers: Identify every TrueConf Server instance (Windows and Linux) and check its version. Affected versions are 5.3.x to 5.3.9, 5.4.x to 5.4.9, 5.5.x to 5.5.5 and anything older. Treat any instance with an unknown version as vulnerable.
      • Close 4307/TCP now: Block inbound 4307/TCP from the internet and from untrusted segments at the perimeter firewall and on host firewalls. Allow only an explicit allowlist of admin hosts. This kills the known attack path immediately.
      • Apply the vendor fix: A patch is available from the vendor — look up the fixed version in the vendor advisory. You need to move to a release outside the affected ranges. Snapshot or back up the configuration and database first.
      • Triage for compromise: On exposed instances, capture volatile data before patching (process list, network connections, scheduled tasks/cron jobs, new local accounts). Preserve TrueConf service logs and system logs going back at least 30 days. If you find evidence of code execution, isolate the host and invoke IR (under NIS2, assess whether the 24 h early-warning obligation applies).
      • Rotate secrets: If an instance was reachable on 4307/TCP from the internet, rotate everything stored on it: admin accounts, LDAP/AD bind accounts, SMTP credentials, API tokens and TLS keys.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Move TrueConf servers into a dedicated DMZ or collaboration zone. If clients don't strictly need 4307/TCP, restrict it to a management VLAN. Open only the media and signalling ports that are actually required.
      • Egress filtering: Limit outbound traffic from the TrueConf host to the destinations it needs (updates, directory, SMTP). This makes reverse shells, payload staging and exfiltration harder after a successful script execution.
      • IPS/NGFW rule: Add a "drop + alert" rule for 4307/TCP sessions from non-allowlisted sources. Until a vendor-specific signature exists, use this Suricata shape: alert tcp !$TRUECONF_ADMIN any -> $TRUECONF_SRV 4307 (msg:"TrueConf 4307 access from non-admin source"; flow:to_server,established; sid:9000001;)
      • Endpoint hardening: Run the TrueConf service under a dedicated low-privilege account rather than SYSTEM or root, where the vendor supports it. On Windows, use AppLocker/WDAC to stop the service process from launching script interpreters (cmd.exe, powershell.exe, wscript.exe, cscript.exe). On Linux, enforce AppArmor/SELinux profiles that deny execve of shells.
      • Access control: If external access is unavoidable, publish the server only via VPN or an authenticating reverse proxy. Never expose 4307/TCP directly.

    3. Runbook step 3

      Detection rules

      • Process ancestry (Sysmon EID 1 / Security 4688 / EDR): Watch for shells or script interpreters spawned by the TrueConf service. KQL: DeviceProcessEvents | where InitiatingProcessFolderPath has "TrueConf" and FileName in~ ("cmd.exe","powershell.exe","pwsh.exe","wscript.exe","cscript.exe","mshta.exe","rundll32.exe")
      • Linux auditd: Flag execve events where ppid or auid belongs to the TrueConf service account and exe is one of /bin/sh, /bin/bash, python*, curl or wget. Rule shape: -a always,exit -F arch=b64 -S execve -F uid=<trueconf_uid> -k trueconf_exec
      • Network telemetry (Zeek/Suricata): Alert on connections to 4307/TCP from outside the allowlist. SPL: index=zeek sourcetype=zeek_conn id.resp_p=4307 NOT [| inputlookup trueconf_admin_allowlist] | stats count values(id.orig_h) by id.resp_h
      • Anomalous egress (Sysmon EID 3): Look for outbound connections from the TrueConf process or its children to unfamiliar external IPs, particularly on 443, 4444, 8080 or high ports.
      • Persistence and file artefacts (Sysmon EID 11/13, Security 4698/4720): Look for new script files (.ps1, .bat, .vbs, .sh) in the TrueConf install or temp directories, new scheduled tasks or cron jobs, and freshly created local accounts on the server.

    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 remote unauthorized attacker with network access via port 4307/TCP to the TrueConf server versions 5.3.X to 5.3.9, 5.4.X to 5.4.9, 5.5.X to 5.5.5, and earlier could execute an arbitrary script by calling an undocumented function.

    Source: pwn.watch, CISA KEV Catalog, cvelistv5, NVD (NIST)

    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
    TrueConfTrueConf Server
    • 5.3 – < 5.3.9
    • < 5.3
    • 5.5 – < 5.5.5
    • 5.4 – < 5.4.9
    • 5.3.9
    • 5.3
    • 5.5.5
    • 5.4.9
    trueconftrueconf_server
    • < 5.3.9.10015
    • < 5.3.9.10013
    • 5.4.0.12689 – < 5.4.9.10072
    • 5.4.0.12700 – < 5.4.9.10019
    • 5.5.0.13828 – < 5.5.5.10009
    • 5.5.0.13826 – < 5.5.5.10010
    • 5.3.9.10015
    • 5.3.9.10013
    • 5.4.9.10072
    • 5.4.9.10019
    • 5.5.5.10009
    • 5.5.5.10010

    Vendors and products

    Weakness classes (CWE)

    • CWE-306Missing Authentication for Critical Function

      Base

      The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.

      Entry at MITRE CWE-306

    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

    References & sources

    • ics-cert.kaspersky.comKLCERT-26-057: TrueConf Server. Missing Authentication for Critical FunctionThird-party advisory
    • securelist.comtr/head-mare-targets-trueconf-server-with-phantomcore/120988related
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-72529government-resource
    • pwn.watchpwn.watch: TrueConf Server: TrueConf Server Code Injection Vulnerabilitypwn-watch
    • trueconf.comTrueConf Server — CVE-2026-72530pwn-watch
    • NVD (NIST)NVD: CVE-2026-72530pwn-watch
    • NVD (NIST)NVD: CVE-2026-72529pwn-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-2026-72529","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-20T17:44:08.693101Z"}
      {"id":"CVE-2026-72529","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-19T00:00:00+00:00"}

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

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentchanged
      {"id":"CVE-2026-72529","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-19T17:15:51.122126Z"}
      {"id":"CVE-2026-72529","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-19T00:00:00+00:00"}

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

    3. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: yes

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://securelist.com/tr/head-mare-targets-trueconf-server-with-phantomcore/120988/
      SSVC assessmentadded
      —
      {"id":"CVE-2026-72529","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-08-19T17:15:51.122126Z"}

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

    4. Receivedkaspersky.com

      CVSS V4.0: AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

      Weakness type: CWE-306

      Description added or changed

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      TrueConf Server
      Descriptionadded
      —
      A remote unauthorized attacker with network access via port 4307/TCP to the TrueConf server versions 5.3.X to 5.3.9, 5.4.X to 5.4.9, 5.5.X to 5.5.5, and earlier could execute an arbitrary script by calling an undocumented function.
      CVSSadded
      —
      AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
      Weakness type (CWE)added
      —
      CWE-306
      Referenceadded
      —
      https://ics-cert.kaspersky.com/advisories/2026/08/11/trueconf-server-missing-authentication-for-critical-function/

      Source identifier: vulnerability@kaspersky.com

    Linked advisories

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