CriticalCVE-2026-25089

    Fortinet FortiSandbox OS Command Injection Vulnerability (CVE-2026-25089)

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

    What is affected, what to do

    An OS command injection vulnerability in Fortinet FortiSandbox allows an unauthenticated attacker to execute unauthorized commands via specially crafted HTTP requests. Affected versions include 4.2.0 to 4.2.8, 4.4.0 to 4.4.9, 5.0.0 to 5.0.6, and the Cloud and PaaS versions 5.0.4 to 5.0.6. The vulnerability is actively exploited in the wild, posing a significant risk to affected systems. An immediate update to version 5.0.7 or higher is urgently recommended to mitigate the threat.

    The vulnerability is being actively exploited; treat it as a priority. Update fortisandbox to version 5.0.6, fortisandbox_cloud to version 5.0.6, fortisandbox_paas to version 5.0.6. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Fortinet FortiSandbox lte 5.0.0..5.0.5
    • Fortinet FortiSandbox lte 4.4.0..4.4.8
    • Fortinet FortiSandbox lte 4.2.1..4.2.8
    • Fortinet FortiSandbox Cloud lte 5.0.4..5.0.5
    • Fortinet FortiSandbox PaaS lte 5.0.4..5.0.5

    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

    9.1

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: pwn.watch, BSI, CVE.org, SingCERT, Fortinet PSIRT

    76.1 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.53

    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
    243.41 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
    9.1
    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
    76.1 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    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
    99.53
    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
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 9 June 2026
    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-78

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication or user interaction and leads straight to OS command execution, which means full compromise of confidentiality, integrity and availability. Its exploitation likelihood ranks among the very highest of all scored CVEs. Fortinet edge and security appliances are favoured targets for initial access and persistence: they rarely run EDR, and they hold trusted integration keys to firewalls and mail gateways. CISA has not flagged ransomware use, but that does not lower the urgency. Treat any instance reachable from the internet or from broad internal networks as a critical emergency to fix within 24 hours, and isolate 4.2 appliances immediately because no fix exists for them. Only tightly segmented instances reachable solely from the admin network justify waiting for the next emergency maintenance window. NIS2 entities should check their reporting obligations if they find indicators of compromise.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory and version check: Enumerate every FortiSandbox instance (hardware, VM, Cloud, PaaS) and confirm the firmware version (get system status in the CLI). Vulnerable versions are 5.0.0–5.0.5, 4.4.0–4.4.8 and all of 4.2.
      • Patch: Upgrade to FortiSandbox 5.0.6 or 4.4.9. The 4.2 branch has no fix. Migrate those appliances to a fixed branch (check the path in the Fortinet Upgrade Path Tool), or take them offline until you can. For FortiSandbox Cloud and PaaS (5.0.4–5.0.5), confirm remediation status with Fortinet support. See the vendor advisory for patch details.
      • Cut exposure now: Remove the HTTP/HTTPS management interface (typically TCP 80/443) from the internet and from user VLANs. Restrict it to a dedicated admin network or a jump-host allowlist. Disable plain HTTP on the management interface by tightening allowaccess under config system interface.
      • Triage before you patch: Preserve the configuration backup and event logs before upgrading. Patching will not evict an implant that is already in place. Review admin accounts, scheduled jobs and config drift against a known-good baseline.
      • Rotate secrets: If the appliance was exposed or looks suspicious, rotate everything stored on it. That covers admin passwords, API tokens, integration keys for FortiGate, FortiMail and FortiClient EMS, LDAP/RADIUS bind accounts, and SMTP and cloud connectors.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Put the FortiSandbox in its own management zone. Allow inbound traffic only from integrated Fortinet devices and the admin network. Apply default-deny egress, with exceptions only for FortiGuard updates and syslog/SIEM. This kills reverse shells and exfiltration paths.
      • Sandbox network separation: Verify that the analysis/guest-VM network (the outgoing port for malware traffic) is strictly separated from the management port. A compromised management plane must not become a bridge into production.
      • IPS/WAF: On upstream FortiGates or reverse proxies, enable IPS signatures for CVE-2026-25089 as soon as FortiGuard ships them. Until then, block HTTP requests to the sandbox interface that carry shell metacharacters in parameters or headers (;, |, `, $(, %3B, %7C, %60, %24%28).
      • IAM / least privilege: Cut local admin accounts to the minimum, set per-admin trusted hosts and enforce MFA on GUI access. Scope integration accounts to the API rights they actually need. None of this stops the unauthenticated bug itself, but it limits what an attacker can do with harvested credentials.
      • Fallback: If you can neither patch nor isolate, shut the sandbox down temporarily. Switch the integrations (FortiGate, FortiMail) to FortiGuard cloud sandboxing, or to fail-open with hardened AV profiles. Record the risk acceptance.

    3. Runbook step 3

      Detection rules

      • FortiSandbox web/event logs (syslog to SIEM): Look for HTTP requests to the management interface from unauthorised sources whose URI or body contains shell metacharacters. KQL sketch: CommonSecurityLog | where DeviceProduct has "FortiSandbox" and RequestURL matches regex @"(%3B|%7C|%60|\$\(|;|\|)"
      • Network telemetry (Zeek/Suricata): Flag outbound connections from the sandbox management IP to unknown external hosts. Pay particular attention to odd ports, long-lived TCP sessions and DNS lookups for OAST/callback domains (*.oast.*, *.interact.sh, *.burpcollaborator.net). Zeek query: conn.log where id.orig_h == <sandbox_mgmt_ip> and resp_h is not on the allowlist.
      • Firewall logs: Watch for inbound hits on TCP 80/443 of the sandbox from the internet or unexpected segments, scanning patterns, and sudden request bursts. Sigma shape: logsource: firewall, dst_ip|cidr: <sandbox>, src_ip|cidr not: <admin_net>, dst_port: [80,443].
      • Admin and config events: Alert on new or modified admin accounts, config changes outside change windows, unexpected reboots or firmware operations, and logins from new source IPs. Check Fortinet event logs of type "admin" and "system" for deviations.
      • Downstream systems: Look for unusual API calls by sandbox integration accounts against FortiGate, FortiMail or EMS, and for LDAP binds by the sandbox bind account from foreign hosts. Either points to credential abuse after a compromise.

    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 improper neutralization of special elements used in an os command ('os command injection') vulnerability in Fortinet FortiSandbox 5.0.0 through 5.0.5, FortiSandbox 4.4.0 through 4.4.8, FortiSandbox 4.2 all versions, FortiSandbox Cloud 5.0.4 through 5.0.5, FortiSandbox PaaS 5.0.4 through 5.0.5 may allow an unauthenticated attacker to execute unauthorized commands via specifically crafted HTTP requests

    Source: pwn.watch, BSI CSAF, BSI WID Portal, CISA KEV Catalog, NVD (NIST), CVE.org (MITRE), CSA/SingCERT, cvelistv5, fortinet_rss

    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
    FortinetFortiSandbox
    • 5.0.0 – ≤ 5.0.5
    • 4.4.0 – ≤ 4.4.8
    • 4.2.1 – ≤ 4.2.8
    • < 5.0.6
    • < 4.4.9
    • —
    • —
    • —
    • 5.0.6
    • 4.4.9
    FortinetFortiSandbox Cloud
    • 5.0.4 – ≤ 5.0.5
    • —
    FortinetFortiSandbox PaaS
    • 5.0.4 – ≤ 5.0.5
    • —
    fortinetfortisandbox
    • 4.2.0 – ≤ 4.2.8
    • 5.0.0 – < 5.0.6
    • 4.4.0 – < 4.4.9
    • —
    • 5.0.6
    • 4.4.9
    fortinetfortisandbox_cloud
    • 5.0.4 – < 5.0.6
    • 5.0.6
    fortinetfortisandbox_paas
    • 5.0.4 – < 5.0.6
    • 5.0.6

    Vendors and products

    Weakness classes (CWE)

    • CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

      Base

      The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

      Entry at MITRE CWE-78

    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-2026-25089 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2026-25089 (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • fortiguard.fortinet.compsirt/FG-IR-26-141pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-25089government-resource
    • pwn.watchpwn.watch: Fortinet FortiSandbox: Fortinet FortiSandbox OS Command Injection Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2026-25089pwn-watch
    • fortiguard.fortinet.comFortinet FortiSandbox — CVE-2026-39808pwn-watch
    • NVD (NIST)NVD: CVE-2026-39808pwn-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).

    One NVD translation into another language is hidden.

    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-2026-25089
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-25089"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-25089.svg?lang=en" alt="CVE-2026-25089 – NEOSEC Intel" height="20"></a>