Read the docs
TI-2021-08059 Aliases CVE-2021-26109GHSA-9h5m-38gw-j896

Integer overflow in Fortinet FortiOS

Priority MEDIUM 47CWE-190Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-190 and the CVSS impact.

Summary

An integer overflow or wraparound vulnerability in the memory allocator of SSLVPN in FortiOS before 7.0.1 may allow an unauthenticated attacker to corrupt control data on the heap via specifically crafted requests to SSLVPN, resulting in potentially arbitrary code execution.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01883 79th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
FortinetFortinet FortiOSFortiOS before 7.0.1—No fix listedCNA
  • Fortinet FortiOS VendorFortinet Affected FortiOS before 7.0.1 Fixed in — No fix listed CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:*6.0.0 – 6.0.12; 6.2.0 – 6.2.9; 6.4.0 – 6.4.5VulnerableFortinet
cpe:2.3:o:fortinet:fortios:7.0.0:*:*:*:*:*:*:*7.0.0VulnerableFortinet
  • cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:* Versions 6.0.0 – 6.0.12; 6.2.0 – 6.2.9; 6.4.0 – 6.4.5 Vulnerable ·Fortinet
  • cpe:2.3:o:fortinet:fortios:7.0.0:*:*:*:*:*:*:* Versions 7.0.0 Vulnerable ·Fortinet

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-26109
  2. 2026-10-03 Alias added: GHSA-9h5m-38gw-j896

References

Patch 1

  • TI-2026-20057 Authentication bypass in Fortinet FortiWeb KEVCVSS 3.1CRITICAL 9.4
  • TI-2025-18911 Heap-based buffer overflow in Fortinet FortiSwitchManager KEVCVSS 3.1CRITICAL 9.8
  • TI-2024-36904 Authentication bypass in Fortinet FortiOS KEVCVSS 3.1CRITICAL 9.8
  • TI-2024-15234 A use of externally-controlled format string in Fortinet FortiOS versions 7.4.0 through… KEVCVSS 3.1CRITICAL 9.8
  • TI-2024-14448 Out-of-bounds write in Fortinet FortiOS KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-12585 Heap-based buffer overflow in Fortinet FortiOS-6K7K KEVCVSS 3.1CRITICAL 9.8
See all 276 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences