FortiOS: Numeric Truncation Error
CVE-2026-126254 is a critical-severity numeric truncation error vulnerability in FortiOS from Fortinet, with a CVSS 3.1 base score of 9.6 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: 8.0.0 through 8.0.1; 7.6.0 through 7.6.7; 7.4.0 through 7.4.12, 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 0.47% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
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 | 8.0.0 through 8.0.1; 7.6.0 through 7.6.7; 7.4.0 through 7.4.12; 7.2.0 through 7.2.13 | 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
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- NoneNo data is disclosed.
- 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:L/UI:N/S:C/C:N/I:H/A:H. Scored by CNA (fortinet.com).
Official description
A numeric truncation error vulnerability in Fortinet FortiOS 8.0.0 through 8.0.1, FortiOS 7.6.0 through 7.6.7, FortiOS 7.4.0 through 7.4.12, FortiOS 7.2.0 through 7.2.13 may allow a configured ibgp neighbor to send malicious/malformed attributes to all connected routers via a specially crafted request
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Numeric Truncation Error
Truncation errors occur when a primitive is cast to a primitive of a smaller size and data is lost in the conversion.
How developers prevent this class of flaw
- Ensure that no casts, implicit or explicit, take place that move from a larger size primitive or a smaller size primitive.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in FortiOS
- 9.8 Critical severity
- 7.5 High severity
- 7.4 High severity
- 7.4 High severity
- 9.3 Critical severity
- 8.1 High severity
Recent Numeric Truncation Error vulnerabilities
- 7.0 High severity
- 9.9 Critical severity
- 7.0 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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