CVE-2026-24858: Fortinet Multiple Products Critical Vulnerability

What is CVE-2026-24858?

An Authentication Bypass Using an Alternate Path or Channel vulnerability [CWE-288] vulnerability in Fortinet FortiAnalyzer 7.6.0 through 7.6.5, FortiAnalyzer 7.4.0 through 7.4.9, FortiAnalyzer 7.2.0 through 7.2.11, FortiAnalyzer 7.0.0 through 7.0.15, FortiManager 7.6.0 through 7.6.5, FortiManager 7.4.0 through 7.4.9, FortiManager 7.2.0 through 7.2.11, FortiManager 7.0.0 through 7.0.15, FortiOS 7.6.0 through 7.6.5, FortiOS 7.4.0 through 7.4.10, FortiOS 7.2.0 through 7.2.12, FortiOS 7.0.0 through 7.0.18, FortiProxy 7.6.0 through 7.6.4, FortiProxy 7.4.0 through 7.4.12, FortiProxy 7.2.0 through 7.2.15, FortiProxy 7.0.0 through 7.0.22, FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 through 7.6.6, FortiWeb 7.4.0 through 7.4.11 may allow an attacker with a FortiCloud account and a registered device to log into other devices registered to other accounts, if FortiCloud SSO authentication is enabled on those devices.

Technical Analysis

Weakness Classification

This vulnerability is classified as CWE-288.

Attack Vector Breakdown

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

Impact Analysis

This vulnerability is exploitable over the network, meaning any system reachable via the internet or internal network is potentially at risk without physical access. The attack complexity is low, requires no special privileges, and needs no user interaction — making it straightforward to exploit at scale. Successful exploitation can result in full confidentiality breach (complete data disclosure), complete integrity compromise (data modification or code execution), total availability loss (denial of service).

Exploitation Probability (EPSS): 4.8% chance of exploitation in the next 30 days (90th percentile). While the base probability may appear low, inclusion in CISA KEV confirms real-world exploitation is already occurring.

Exploit Availability

Public exploit code or proof-of-concept is available for CVE-2026-24858. This significantly increases the risk of exploitation, as attackers can use or adapt existing exploit code rather than developing their own. A public exploit reference has been identified. Organizations should treat this as an urgent patching priority.

Is CVE-2026-24858 being exploited?

Yes. CVE-2026-24858 is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, restricted to CVEs with confirmed active exploitation in the wild. CISA added this vulnerability on 2026-01-27. Inclusion in KEV triggers the patching mandate under BOD 22-01 for U.S. federal civilian agencies, with a remediation deadline of 2026-01-30. Additionally, public exploit code is available, which lowers the barrier for attackers.

How to fix CVE-2026-24858

Upgrade FortiOS or the affected product firmware to the fixed version listed in the FortiGuard PSIRT advisory. For FortiGate devices, use the firmware upgrade path tool to determine the correct upgrade sequence. If immediate patching is not possible, apply the recommended workaround (e.g. disabling affected features, restricting management interface access). Check the Fortinet PSIRT Advisories page for the specific patch or update. CISA's Known Exploited Vulnerabilities catalog requires U.S. federal agencies to remediate this vulnerability by the due date shown below under Binding Operational Directive 22-01. Private organizations should treat KEV entries as priority-one patches because active exploitation has been confirmed in the wild.

Related Vulnerabilities

Other actively exploited vulnerabilities affecting Multiple Products or sharing the same weakness (CWE-288):

• CVE-2025-59718 (Critical 9.8) [same product] — A improper verification of cryptographic signature vulnerability in Fortinet…
• CVE-2025-32756 (Unknown N/A) [same product] — Fortinet FortiFone, FortiVoice, FortiNDR and FortiMail contain a stack-based…
• CVE-2025-43510 (High 7.8) [same product] — A memory corruption issue was addressed with improved lock state checking…
• CVE-2025-43520 (Medium 5.5) [same product] — A memory corruption issue was addressed with improved memory handling. This…
• CVE-2025-31277 (High 8.8) [same product] — The issue was addressed with improved memory handling. This issue is fixed in…

Frequently asked questions

Is CVE-2026-24858 critical?

CVE-2026-24858 has a CVSS 3.1 base score of 9.8 — Critical severity. It should be treated as a priority patch, especially given the active exploitation confirmed by CISA. The availability of public exploit code further increases the urgency.

Is CVE-2026-24858 being actively exploited?

Yes — CISA added CVE-2026-24858 to the Known Exploited Vulnerabilities catalog on 2026-01-27. Inclusion in KEV means CISA has confirmed in-the-wild exploitation. Public exploit code has also been identified, making exploitation accessible to a broader range of threat actors.

How do I patch CVE-2026-24858?

Apply the security update from Fortinet for Multiple Products. Federal agencies must remediate by 2026-01-30 under BOD 22-01. Refer to the Fortinet PSIRT Advisories for the official patch.

What type of vulnerability is CVE-2026-24858?

CVE-2026-24858 is classified under CWE-288.

What is the CVSS score for CVE-2026-24858?

CVE-2026-24858 has a CVSS 3.1 base score of 9.8, classifying it as Critical severity. The attack vector is Network, attack complexity is Low, and no privileges are required.