Critical Fortinet FortiOS bug CVE-2024-21762 potentially impact 150,000 internet
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2024-21762 | Out-of-Bounds Write RCE in Fortinet FortiOS and FortiProxy CVE-2024-21762 is a critical (CVSS 9.8) out-of-bounds write (CWE-787) in the SSL VPN functionality of Fortinet FortiOS and FortiProxy, allowing an unauthenticated remote attacker to execute unauthorized code or commands by sending specifically crafted requests to the vulnerable service. No authentication or user interaction is required, and network access to the SSL VPN interface is the only precondition. Organizations running affected FortiOS versions (on FortiGate appliances) or any affected FortiProxy version are exposed, particularly where the SSL VPN is internet-facing. The flaw is actively exploited: it was added to CISA's Known Exploited Vulnerabilities catalog on 2024-02-09 with ransomware use noted, EPSS puts the 30-day exploitation probability at 84.3%, and public scans suggest roughly 150,000 internet-exposed Fortinet devices may be impacted. Do: Upgrade FortiOS and FortiProxy to fixed releases outside the affected ranges per Fortinet's advisory, prioritizing internet-facing devices; as an interim mitigation, disable SSL VPN (or SSL VPN web mode) where it is not required, per vendor and CISA guidance. After patching, check for signs of compromise and rotate credentials, since Fortinet has warned that attackers retained access to FortiGate devices post-patching. The flaw is in CISA KEV with known ransomware use, so treat this as an urgent patching priority. | 9.8 | 84% | KEV ransomware |
| mass≈150,000 internet-exposed FortiGate/FortiProxy devices (public internet-wide scans) |
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Researchers warn that the critical vulnerability CVE-2024-21762 in Fortinet FortiOS could potentially impact 150,000 exposed devices.
In February, Fortinet warned that the critical remote code execution vulnerability CVE-2024-21762 (CVSS score 9.6) in FortiOS SSL VPN was actively exploited in attacks in the wild.
The security firm did not provide details about the attacks exploiting this vulnerability.
The issue is an out-of-bounds write vulnerability that can be exploited by sending specially crafted HTTP requests to vulnerable instances. The vendor recommends to disable SSL VPN as a workaround.
“A out-of-bounds write vulnerability [CWE-787] in FortiOS may allow a remote unauthenticated attacker to execute arbitrary code or command via specially crafted HTTP requests.” reads the advisory.
“Workaround : disable SSL VPN (disable webmode is NOT a valid workaround). Note: This is potentially being exploited in the wild.”
The following table includes the list of the impacted versions and the available versions that solve the issue.
| Version | Affected | Solution |
|---|---|---|
| FortiOS 7.6 | Not affected | Not Applicable |
| FortiOS 7.4 | 7.4.0 through 7.4.2 | Upgrade to 7.4.3 or above |
| FortiOS 7.2 | 7.2.0 through 7.2.6 | Upgrade to 7.2.7 or above |
| FortiOS 7.0 | 7.0.0 through 7.0.13 | Upgrade to 7.0.14 or above |
| FortiOS 6.4 | 6.4.0 through 6.4.14 | Upgrade to 6.4.15 or above |
| FortiOS 6.2 | 6.2.0 through 6.2.15 | Upgrade to 6.2.16 or above |
| FortiOS 6.0 | 6.0 all versions | Migrate to a fixed release |
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog.
This week, researchers at the Shadowserver Foundation announced that nearly 150,000 devices are still potentially impacted by the issue despite Fortinet added it to the catalog.
The researchers scanned the Internet for Internet-facing Fortinet FortiOS and FortiProxy secure web gateway systems vulnerable to CVE-2024-21762.
150 000 found on 2024-03-06 of course (not 2024-02-06)
— Shadowserver (@Shadowserver) March 7, 2024
The majority of vulnerable devices (at March 9, 2024) are in the United States (24.647), followed by India (7.713), and Brazil (4.934).
Researchers from GreyNoise also published an interesting analysis on the bug, titled “Hunting for Fortinet CVE-2024-21762: Vulnerability Research for Detection Engineering.”
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