CVE-2024-21762: Fortinet FortiOS Out-of-Bound Write Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Fortinet FortiOS. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2024-02-09, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2024-02-16; treat that as the outer limit, not the target. CISA also lists it as known to be used in ransomware campaigns.
• EPSS 83.4%, percentile 99.7: FIRST’s model estimates a 83.4% chance of exploitation activity in the next 30 days, higher than 99.7% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Editorial verdict: Act now. FortiOS SSL VPN Pre-Auth RCE (CVE-2024-21762) — Any FortiGate or FortiProxy with SSL VPN enabled on an unfixed build is exposed to unauthenticated remote code execution that has been exploited; upgrade or disable SSL VPN today.

What it is

A out-of-bounds write in Fortinet FortiOS versions 7.4.0 through 7.4.2, 7.2.0 through 7.2.6, 7.0.0 through 7.0.13, 6.4.0 through 6.4.14, 6.2.0 through 6.2.15, 6.0.0 through 6.0.17, FortiProxy versions 7.4.0 through 7.4.2, 7.2.0 through 7.2.8, 7.0.0 through 7.0.14, 2.0.0 through 2.0.13, 1.2.0 through 1.2.13, 1.1.0 through 1.1.6, 1.0.0 through 1.0.7 allows attacker to execute unauthorized code or commands via specifically crafted requests

CISA’s summary

Fortinet FortiOS contains an out-of-bound write vulnerability that allows a remote unauthenticated attacker to execute code or commands via specially crafted HTTP requests.

Weakness type: CWE-787.

Product: Fortinet FortiOS · Assigned by: fortinet · Published: 2024-02-09

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2024-02-09; federal due date 2024-02-16. Known ransomware use: Known.
• CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
• CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 83.43% probability of exploitation activity in the next 30 days; percentile 99.7.

Timeline

• 2024-02-08 — erroneo.us brief: FortiOS SSL VPN Pre-Auth RCE (CVE-2024-21762)
• 2024-02-09 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2024-02-09 — CVE record published by fortinet
• 2024-02-16 — CISA remediation deadline for US federal agencies
• 2026-08-04 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (fortiguard.fortinet.com) fortiguard.fortinet.com

Vulnerability records

1. CVE.org record CVE-2024-21762 cve.org
2. NVD entry CVE-2024-21762 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. fortiguard.com fortiguard.com

All exploited Fortinet vulnerabilities · Today’s Security Digest