Fortinet FortiOS Out-of-Bound Write
CVE-2024-21762 is a critical-severity out-of-bounds write vulnerability in FortiOS from Fortinet, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 6.2.16, 6.4.15, 7.0.14 as the first without the flaw, so updating FortiOS to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on February 9, 2024, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update FortiOS to 6.2.16 or 6.4.15 or 7.0.14 or 7.2.7, whichever matches your release line, or a later version.
- Update FortiProxy to 2.0.14 or 7.0.15 or 7.2.9 or 7.4.3, whichever matches your release line, or a later version.
- CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Read the advisory on fortiguard.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Fortinet | FortiOS | 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 6.0.18; 6.0.0 up to, but not including, 6.2.16; 6.4.0 up to, but not including, 6.4.15; and 3 more ranges | 6.2.16, 6.4.15, 7.0.14, 7.2.7, 7.4.3 |
| Fortinet | FortiProxy | 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; 1.2.1 through 1.2.13; 01.02.00; 1.1.4 through 1.1.6; 01.01.00 through 01.01.03; and 5 more ranges | 2.0.14, 7.0.15, 7.2.9, 7.4.3 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CNA (fortinet.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
A out-of-bounds write vulnerability in Fortinet FortiOS 7.4.0 through 7.4.2, FortiOS 7.2.0 through 7.2.6, FortiOS 7.0.0 through 7.0.13, FortiOS 6.4.0 through 6.4.14, FortiOS 6.2.0 through 6.2.15, FortiOS 6.0 all versions, FortiProxy 7.4.0 through 7.4.2, FortiProxy 7.2.0 through 7.2.8, FortiProxy 7.0.0 through 7.0.14, FortiProxy 2.0.0 through 2.0.13, FortiProxy 01.02 all versions, FortiProxy 1.2 all versions, FortiProxy 01.01 all versions, FortiProxy 1.1 all versions, FortiProxy 01.00 all versions allows attacker to execute unauthorized code or commands via specifically crafted requests
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-21762US Government Resource
Other vulnerabilities in FortiOS
- 9.8 Critical severity
- 7.5 High severity
- 7.4 High severity
- 7.4 High severity
- 9.6 Critical severity
- 9.3 Critical severity
Recent Out-of-bounds Write vulnerabilities
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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