Fortinet Multiple Products Heap-based Buffer Overflow Vulnerability (CVE-2025-25249)
Published Last modified In CISA KEV since Sources: Siemens ProductCERT, BSI, CVE.org
What is affected, what to do
A heap-based buffer overflow vulnerability in Fortinet FortiOS, FortiSwitchManager, and FortiSASE allows an attacker to execute unauthorized code via specially crafted packets. This affects FortiOS versions 6.4 through 7.6.4, FortiSwitchManager versions 7.0 through 7.2.7, and FortiSASE. The vulnerability is actively exploited in the wild. Immediate patching to the latest versions is imperative to mitigate the risk.
The vulnerability is being actively exploited; treat it as a priority. Update fortiswitchmanager to version 7.0.6, FortiOS to version 6.4.17. Immediate actions, mitigation and detection rules are in the runbook below.
- Affected
- Fortinet FortiSwitchManager
lte 7.2.2..7.2.5 - Fortinet FortiOS
lte 7.6.0..7.6.2 - Fortinet FortiOS
lte 7.4.0..7.4.7 - Fortinet FortiOS
lte 7.2.4..7.2.11
- Fortinet FortiSwitchManager
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Metrics
9.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
7.4
CVSS v3
Severity High on the scale from 0 to 10.
Source: Siemens ProductCERT, BSI, CVE.org
3.8 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 89.9
Show all metrics
- Severity
- Critical
Priority score
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- 215.35
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 exploited (KEV)Source: VulnCheck KEV (opens in a new tab)
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
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- 7.4
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- 3.8 %
- 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- 89.9
- 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 glossaryCWE
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-122
Response and mitigation
Why act now?
Prioritisation rationale
This flaw gives an unauthenticated, network-reachable attacker code execution on a perimeter device with no user interaction, which puts it in the most critical class. Fortinet firewalls and VPN gateways are a recurring target because they sit at the network edge and hold VPN credentials and directory-service bindings. CISA does not flag known ransomware use, but exploitation likelihood is rated well above average. Organisations in NIS2 or KRITIS scope with internet-facing FortiGates should treat this as top priority and patch within 24 hours. Any remaining FortiOS 6.4 estate should be escalated to risk owners as unpatchable exposure.
Runbook step 1
Immediate response (0-24 h)
- Inventory: Enumerate every FortiGate, FortiSwitchManager and FortiSASE tenant and record the firmware build (
get system status). Affected versions are FortiOS 7.6.0–7.6.3, 7.4.0–7.4.8, 7.2.0–7.2.11, 7.0.0–7.0.17, every FortiOS 6.4 release, FortiSwitchManager 7.2.0–7.2.6 and FortiSwitchManager 7.0.0–7.0.5. - Patch: Vendor fixes are available for FortiOS 7.0/7.2/7.4/7.6 and FortiSwitchManager 7.0/7.2. Look up the exact fixed build in the Fortinet PSIRT advisory for CVE-2025-25249, because NVD and CPE ranges differ slightly. Patch internet-facing units first.
- FortiOS 6.4: No fix is listed for this branch. Raise an emergency change to migrate to a supported branch. Until then, the compensating controls below are mandatory, not optional.
- FortiSASE: Fortinet operates this platform. Get written confirmation of remediation from Fortinet support or the service status page and file it as audit evidence.
- Shrink exposure: Remove HTTPS, SSH and HTTP admin access from WAN interfaces now (
config system interface→set allowaccesswithout those services). Disable unused services on external interfaces, such as SSL-VPN, FortiLink/FortiManager access and CAPWAP. - Preserve evidence before patching: Back up the running config and crash logs (
diagnose debug crashlog read). Patching does not remove persistence an attacker has already established.
- Inventory: Enumerate every FortiGate, FortiSwitchManager and FortiSASE tenant and record the firmware build (
Runbook step 2
Mitigation layers
- Network segmentation: Allow management of FortiGate and FortiSwitchManager only from a dedicated admin VLAN or jump host. Enforce this with local-in policies (
config firewall local-in-policy) that permit management and control-plane ports from approved source networks only. - Attack surface: The advisory says only "specially crafted packets" and does not name the vulnerable service. Treat every externally reachable daemon as in scope. Keep the SSL-VPN portal and admin interface off the open internet where possible, and prefer certificate-authenticated IPsec for remote access.
- IPS and upstream filtering: Update FortiGuard IPS signatures and check whether Fortinet has published a signature for this CVE. Add upstream router ACLs and geo-IP filtering in front of device interfaces.
- IAM and least privilege: Audit admin accounts, remove stale ones and enforce MFA for all administrators. If compromise is suspected, rotate local admin passwords, VPN PSKs, LDAP/RADIUS bind accounts and any certificates stored on the device.
- Egress control: Restrict traffic originating from the device itself to FortiGuard, NTP, DNS, syslog and SIEM destinations. Block and alert on everything else.
- Logging: Forward system, VPN and admin event logs off-box via syslog or FortiAnalyzer, so indicators survive if the attacker tampers with local logs.
- Network segmentation: Allow management of FortiGate and FortiSwitchManager only from a dedicated admin VLAN or jump host. Enforce this with local-in policies (
Runbook step 3
Detection rules
- Daemon crashes: Unexpected process crashes or reboots in crash logs and system event logs (
type=event subtype=system) are a classic by-product of failed heap-overflow attempts. SPL:index=fortigate type=event subtype=system (msg="*crash*" OR msg="*signal 11*") | stats count by devname, msg - Admin and config changes: Alert on new admin accounts,
allowaccesschanges, new local-in or firewall policies, and new local VPN users that have no matching change ticket. Sigma shape:logsource: fortios/event, withaction: Addandcfgpathinsystem.adminoruser.local. - Device-originated outbound traffic: In Zeek or NetFlow, flag sessions sourced from FortiGate interface IPs to non-allowlisted destinations, especially on odd ports or with long-lived connections. KQL:
CommonSecurityLog | where SourceIP in (fortigate_ips) and DestinationIP !in (allowlist) - Malformed traffic to device interfaces: Use Suricata or Zeek to spot bursts of malformed or oversized packets from a single source aimed at FortiGate interfaces. Correlate these with crash timestamps.
- Integrity check: Run Fortinet's firmware and filesystem integrity checks. Hunt for persistence patterns seen in earlier FortiOS compromises, such as symlinks in SSL-VPN language directories. Diff the running config and user list against a known-good backup.
- Daemon crashes: Unexpected process crashes or reboots in crash logs and system event logs (
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 heap-based buffer overflow vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11, FortiOS 7.0.0 through 7.0.17, FortiOS 6.4 all versions, FortiSwitchManager 7.2.0 through 7.2.6, FortiSwitchManager 7.0.0 through 7.0.5 allows attacker to execute unauthorized code or commands via specially crafted packets
Source: siemens_advisory, BSI CSAF, BSI WID Portal, NVD (NIST), CISA KEV Catalog, cvelistv5
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Fortinet | FortiSwitchManager |
|
|
| fortinet | fortisase |
|
|
| fortinet | fortiswitchmanager |
|
|
| Fortinet | FortiOS |
|
|
Affected operating systems
| Family | Vendor | Product | Version |
|---|---|---|---|
| Mobile | fortinet | fortios | — |
| Other | siemens | ruggedcom_ape1808_firmware | — |
| Operating system | Fortinet | FortiOS | 7.6.2 |
Weakness classes (CWE)
CWE-122Heap-based Buffer Overflow
Variant
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Entry at MITRE CWE-122
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.
| Source | Reference | Maturity | Published |
|---|---|---|---|
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited (KEV) |
References & sources
- fortiguard.fortinet.compsirt/FG-IR-25-084
- Siemens ProductCERTproductcert/html/ssa-864900.html
- socradar.ioblog/cve-2025-25249-pivotc2-fortigate-ratThird-party advisory
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-25249government-resource
Reanalysis & status changes
Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.
CVE Modified134c704f-9b21-4f2e-91b3-4a467353bcc0
- SSVC:
before {"id":"CVE-2025-25249","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technica… - SSVC: after {"id":"CVE-2025-25249","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technica…
- SSVC:
Modified Analysisnvd@nist.gov
- CPE Configuration: after AND OR *cpe:2.3:o:siemens:ruggedcom_ape1808_firmware:-:*:*:*:*:*:*:* OR cpe:2.3:h:siemens:ruggedcom_ape1808:-:*:*:*:*:*:*:*
- CPE Configuration:
before OR *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 7.6.0 up to (excluding) 7.6.4 *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 7.0.0 up to (excluding) 7.0.18 *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 7.2.0 up to (excluding) 7.2.12 *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 7.4.0 up to (excluding) 7.4.9 *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 6.4.0 up to (excluding) 6.4.17after OR *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 7.6.0 up to (excluding) 7.6.4 *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 7.2.0 up to (excluding) 7.2.12 *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 7.4.0 up to (excluding) 7.4.9 *cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* versions from (including) 6.4.0 up to (excluding) 7.0.18 - Reference Type:
before Fortinet, Inc.: https://fortiguard.fortinet.com/psirt/FG-IR-25-084 Types: Vendor Advisoryafter Fortinet, Inc.: https://fortiguard.fortinet.com/psirt/FG-IR-25-084 Types: Mitigation, Vendor Advisory - Reference Type: after CISA-ADP: https://socradar.io/blog/cve-2025-25249-pivotc2-fortigate-rat/ Types: Exploit, Third Party Advisory
CVE Modified134c704f-9b21-4f2e-91b3-4a467353bcc0
- SSVC:
before {"id":"CVE-2025-25249","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technica…after {"id":"CVE-2025-25249","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technica…
- SSVC:
CVE CISA KEV Update9119a7d8-5eab-497f-8521-727c672e3725
- Date Added: after 2026-09-09
- Due Date: after 2026-09-09
- Required Action: after 2026-09-09
- Vulnerability Name: after 2026-09-09