CVE-2025-25255VulnerabilityPublished 14 Oct 2025Updated 14 Jan 2026

CVE-2025-25255: Fortinet FortiOS · Improper access control

Affects Fortinet FortiOSSource CVE Database V5

Not known to be exploited · CVSS 4.8 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

4.8Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C

Base metrics

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Temporal metrics

Exploit Code Maturity: Proof-of-Concept
Remediation Level: Official Fix
Report Confidence: Confirmed

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.
Exploit Code Maturity: Proof-of-Concept: Proof-of-concept exploit code is available, or an attack demonstration is not practical for most systems. The code or technique is not functional in all situations and may require substantial modification by a skilled attacker.
Remediation Level: Official Fix: A complete vendor solution is available. Either the vendor has issued an official patch, or an upgrade is available.
Report Confidence: Confirmed: Detailed reports exist, or functional reproduction is possible (functional exploits may provide this). Source code is available to independently verify the assertions of the research, or the author or vendor of the affected code has confirmed the presence of the vulnerability.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Fortinet FortiOS	Affected =7.6.0	Fixed in–

AI-suggested

1. Apply vendor patches and updates as soon as they become available for all affected FortiOS and FortiProxy versions. Monitor Fortinet advisories closely for patch releases. 2. Implement strict network segmentation and access controls to limit exposure of Fortinet proxy devices to untrusted networks. 3. Deploy advanced network traffic monitoring and anomaly detection systems to identify unusual HTTP request patterns that may indicate attempts to bypass domain fronting protections. 4. Review and tighten proxy and firewall policies to restrict allowed HTTP headers and domain names, reducing the risk of crafted requests exploiting this vulnerability. 5. Conduct regular security audits and penetration tests focusing on proxy and domain fronting controls to validate the effectiveness of mitigations. 6. Educate security operations teams about this vulnerability to improve detection and response capabilities. 7. Consider deploying additional layers of security such as web application firewalls (WAFs) and intrusion prevention systems (IPS) that can detect and block suspicious proxy traffic. 8. Maintain an inventory of all Fortinet devices and their firmware versions to ensure timely patch management and vulnerability tracking.

Description

An Improperly Implemented Security Check for Standard vulnerability [CWE-358] vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiProxy 7.6.0 through 7.6.3, FortiProxy 7.4.0 through 7.4.11, FortiProxy 7.2 all versions, FortiProxy 7.0.1 through 7.0.22 may allow an unauthenticated proxy user to bypass the domain fronting protection feature via crafted HTTP requests.

Impact

For European organizations, this vulnerability poses a risk primarily to the integrity of network traffic passing through Fortinet FortiOS and FortiProxy devices. Attackers could exploit this flaw to bypass domain fronting protections, potentially allowing unauthorized traffic routing or evasion of security policies. This could facilitate further attacks such as data exfiltration, command and control communication, or lateral movement within networks. While confidentiality and availability are not directly impacted, the integrity compromise can undermine trust in network security controls and complicate incident response. Organizations in sectors with stringent security requirements—such as finance, government, telecommunications, and critical infrastructure—may face increased risk due to the reliance on Fortinet devices for perimeter and proxy security. The lack of authentication requirement increases the attack surface, enabling remote exploitation from external networks. However, the absence of known exploits in the wild and the medium severity rating suggest that immediate widespread exploitation is unlikely but should not be discounted. The vulnerability could be leveraged as part of a multi-stage attack chain by sophisticated threat actors targeting European enterprises.

References

fortiguard.fortinet.com/psirt/FG-IR-24-372 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Jan 2026, 14:55 UTC

Technical details

References

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