FortiOS: Stack-based Buffer Overflow
CVE-2025-53843 is a high-severity stack-based buffer overflow vulnerability in FortiOS from Fortinet, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected FortiOS versions: 7.6.0 through 7.6.3; 7.4.0 through 7.4.8; 7.2.0 through 7.2.12, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of FortiOS you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on fortiguard.fortinet.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Fortinet | FortiOS | 7.6.0 through 7.6.3; 7.4.0 through 7.4.8; 7.2.0 through 7.2.12; 7.0.0 through 7.0.18; 6.4.0 through 6.4.16 | Not stated |
| Siemens | RUGGEDCOM APE1808 | all versions | Not stated |
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
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- LowA basic user account is enough.
- 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:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (fortinet.com).
Official description
A stack-based buffer overflow vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2 all versions, FortiOS 7.0 all versions, FortiOS 6.4 all versions allows attacker to execute unauthorized code or commands via specially crafted packets
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Stack-based Buffer Overflow
The product writes past the end of a buffer that was allocated on the stack.
How developers prevent this class of flaw
- 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.
- Use an abstraction library to abstract away risky APIs. Not a complete solution.
- Implement and perform bounds checking on input.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
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 Stack-based Buffer Overflow vulnerabilities
- 7.2 High severity
- 7.2 High severity
- 7.3 High severity
- 8.8 High severity
- 8.4 High severity
- 7.5 High severity
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