Under non-default configuration, a stack-based buffer overflow in FortiOS version 6.0.10 and below, version 5.6.12 and below may allow a remote attacker authenticated to the SSL VPN to crash the FortiClient NAC daemon (fcnacd) and potentially execute arbitrary code via requesting a large FortiClient file name. We are not aware of proof of concept code successfully achieving the latter.
CVSS v4.0 Metrics
Exploitability
Attack VectorNetwork
ComplexityLow
RequirementsPresent
PrivilegesLow
User InteractionNone
Threat
Exploit MaturityPoC
Vulnerable System
ConfidentialityNone
IntegrityLow
AvailabilityLow
Subsequent System
ConfidentialityNone
IntegrityNone
AvailabilityNone
Supplemental
SafetyNegligible
AutomatableYes
RecoveryAutomatic
Value DensityConcentrated
UrgencyMedium
Change Log
| Date | Source | Changes | Score |
|---|
| 2026-07-21 | PoC | E: U→P | 0.6 → 1.3 |
| 2026-07-21 | cve.org | initial, patch: Unavailable | 0.6 |
Affected Software
| Vendor | Product | Version |
|---|
| Fortinet | FortiOS | ≥ 6.0.0, ≤ 6.0.10 |
| Fortinet | FortiOS | ≥ 5.6.0, ≤ 5.6.12 |
| fortinet | fortios | ≥ 6.0.0, < 6.0.11 |
| fortinet | fortios | < 5.6.13 |
Published: 2024-12-19
