CVE-2021-26109

published 2021-12-08

CVE-2021-26109: 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…

Priority P2 61 critical 9.8 CVSS 3.1

AV N AC L PR N UI N S U C H I H A H

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.

Affected

6 ranges

Vendor	Product	Version range	Fixed in
fortinet	fortinet_fortios	—	—
fortinet	fortios	—	—
fortinet	fortios	—	—
fortinet	fortios	6.0.0 – 6.0.12	—
fortinet	fortios	6.2.0 – 6.2.9	—
fortinet	fortios	6.4.0 – 6.4.5	—

Detection & IOCs extracted from sources · hover to see the quote

• → Target attack surface is the SSLVPN memory allocator in FortiOS; monitor for anomalous or malformed requests directed at the SSLVPN endpoint that may trigger integer overflow/wraparound in heap allocation ↗
• → Attacker is unauthenticated — no valid session or credentials required; detection should cover pre-auth traffic to SSLVPN listeners, not just authenticated sessions ↗
• → CWE-190 (Integer Overflow or Wraparound) in the heap allocator path; look for crash/core dumps, unexpected process restarts, or memory corruption indicators in FortiOS SSLVPN daemon logs ↗

• · Vulnerability affects FortiOS versions before 7.0.1; ensure patching to 7.0.1 or later. All unpatched FortiOS SSLVPN deployments exposed to untrusted networks are at risk from unauthenticated attackers. ↗

CVSS provenance

nvd v3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd v2.0 7.5 HIGH AV:N/AC:L/Au:N/C:P/I:P/A:P

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CWE-190