Is CVE-2021-42756 actively exploited?

No active exploitation of CVE-2021-42756 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-42756 be exploited remotely?

Yes. CVE-2021-42756 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-42756?

CVE-2021-42756 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2021-42756

CWE-121Published: February 16, 2023· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official Description

Multiple stack-based buffer overflow vulnerabilities [CWE-121] in the proxy daemon of FortiWeb 5.x all versions, 6.0.7 and below, 6.1.2 and below, 6.2.6 and below, 6.3.16 and below, 6.4 all versions may allow an unauthenticated remote attacker to achieve arbitrary code execution via specifically crafted HTTP requests.

NVD Source

Technical Analysis

CVE-2021-42756 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.