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Fortinet has confirmed a brand new, actively exploited essential FortiCloud single sign-on (SSO) authentication bypass vulnerability, tracked as CVE-2026-24858, and says it has mitigated the zero-day assaults by blocking FortiCloud SSO connections from units working susceptible firmware variations.

The flaw permits attackers to abuse FortiCloud SSO to achieve administrative entry to FortiOS, FortiManager, and FortiAnalyzer units registered to different prospects, even when these units have been totally patched in opposition to a beforehand disclosed vulnerability.

The affirmation comes after Fortinet prospects reported compromised FortiGate firewalls on January 21, with attackers creating new native administrator accounts by way of FortiCloud SSO on units working the newest out there firmware.

The assaults have been initially considered via a patch bypass for CVE-2025-59718, a beforehand exploited essential FortiCloud SSO authentication bypass flaw that was patched in December 2025.

Fortinet admins reported that the hackers have been logging into FortiGate units by way of FortiCloud SSO utilizing the e-mail tackle cloud-init@mail.io, then creating new native admin accounts.

Logs shared by impacted prospects confirmed related indicators noticed throughout December exploitation.

On January 22, cybersecurity agency Arctic Wolf confirmed the assaults, saying the assaults appeared automated, with new rogue admin and VPN-enabled accounts created and firewall configurations exfiltrated inside seconds. Arctic Wolf mentioned the assault appeared much like a earlier marketing campaign exploiting CVE-2025-59718 in December.

Fortinet confirms alternate assault path

On January 23, Fortinet confirmed that attackers have been exploiting an alternate authentication path that remained even on totally patched techniques.

Fortinet CISO Carl Windsor mentioned the corporate had noticed instances wherein units working the newest firmware have been compromised, indicating {that a} new assault path was being exploited.

Whereas Fortinet mentioned exploitation had solely been seen via FortiCloud SSO, it warned that the problem additionally applies to different SAML-based SSO implementations.

“It is very important observe that whereas, presently, solely exploitation of FortiCloud SSO has been noticed, this subject is relevant to all SAML SSO implementations,” defined Fortinet.

On the time, Fortinet suggested prospects to limit administrative entry to their units and disable FortiCloud SSO as a mitigation.

The advisory states that Fortinet took actions to mitigate the assaults whereas patches are being developed.

• On January 22, Fortinet disabled FortiCloud accounts that have been being abused by the attackers.
• On January 26, Fortinet disabled FortiCloud SSO globally on the FortiCloud aspect to stop additional abuse.
• On January 27, FortiCloud SSO entry was restored however restricted in order that units working susceptible firmware can not authenticate by way of SSO.

Fortinet says this server-side change successfully blocks exploitation even when FortiCloud SSO stays enabled on affected units, so there’s nothing that must be accomplished client-side till patches are launched.

On January 27, Fortinet additionally printed a formal PSIRT advisory assigning CVE-2026-24858 to the flaw, score it essential with a CVSS rating of 9.4.

The vulnerability is “Authentication Bypass Utilizing an Alternate Path or Channel,” brought on by improper entry management in FortiCloud SSO.

In line with the advisory, attackers with a FortiCloud account and a registered system might authenticate to different prospects’ units if FortiCloud SSO was enabled.

Whereas FortiCloud SSO shouldn’t be enabled by default, Fortinet says it would mechanically activate when a tool is registered with FortiCare, until it’s manually disabled afterward.

Fortinet confirmed the vulnerability was exploited within the wild by the next two malicious FortiCloud SSO accounts, which have been locked out on January 22.

cloud-noc@mail.io
cloud-init@mail.io

Fortinet says that when a tool was breached, they might obtain buyer config recordsdata and create one of many following admin accounts:

audit
backup
itadmin
secadmin
help
backupadmin
deploy
remoteadmin
safety
svcadmin
system

Connections have been seen comprised of the next IP addresses:

104.28.244.115
104.28.212.114
104.28.212.115
104.28.195.105
104.28.195.106
104.28.227.106
104.28.227.105
104.28.244.114

Extra IPs noticed by a 3rd occasion, not Fortinet:

37[.]1.209.19
217[.]119.139.50

The corporate says patches are nonetheless in growth, together with for FortiOS, FortiManager, and FortiAnalyzer.

Till then, FortiCloud SSO is obstructing logins from susceptible units, so directors don’t must disable the characteristic to stop exploitation.

Nonetheless, Fortinet mentioned this might be abused with different SAML SSO implementations, admins could wish to disable the SSO characteristic in the meanwhile with the next command:

config system international
    set admin-forticloud-sso-login disable
finish

Fortinet additionally mentioned it nonetheless investigating whether or not FortiWeb and FortiSwitch Supervisor are affected by the flaw.

The corporate warns that prospects who detect the above indicators of compromise of their logs ought to deal with their units as totally compromised.

Fortinet recommends reviewing all administrator accounts, restoring configurations from known-clean backups, and rotating all credentials.

Whether or not you are cleansing up outdated keys or setting guardrails for AI-generated code, this information helps your staff construct securely from the beginning.

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