Predictive Vulnerability Intelligence.

Product

  • Product
  • Pricing
  • Documentation

Company

  • About
  • Partnerships
  • Blog
  • Support

Legal

  • Terms
  • Privacy
  • Data Licensing

© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2021-42756

51
FAUCET Score

CVE-2021-42756 describes multiple stack-based buffer overflow vulnerabilities in the proxy daemon of FortiWeb versions 5.x, 6.0.7 and below, 6.1.2 and below, 6.2.6 and below, and all 6.4 versions. This critical vulnerability (CVSS 9.8) allows an unauthenticated remote attacker to achieve arbitrary code execution through specially crafted HTTP requests. While not currently listed in KEV, its high EPSS score and significant community discussion (12 mentions) indicate a high potential for exploitation. There are no public exploits available in Metasploit, Nuclei, or ExploitDB, but media coverage confirms Fortinet has released patches.

Impacted Technologies

VendorProductVersion(s)CPE
>= 5.6.0, < 6.0.8CPE matchmatch criteria
cpe:2.3:a:fortinet:fortiweb:*:*:*:*:*:*:*:*
>= 6.1.0, < 6.1.3CPE matchmatch criteria
cpe:2.3:a:fortinet:fortiweb:*:*:*:*:*:*:*:*
>= 6.2.0, < 6.2.7CPE matchmatch criteria
cpe:2.3:a:fortinet:fortiweb:*:*:*:*:*:*:*:*
>= 6.3.0, < 6.3.17CPE matchmatch criteria
cpe:2.3:a:fortinet:fortiweb:*:*:*:*:*:*:*:*
>= 6.4.0, <= 6.4.2CPE matchmatch criteria
cpe:2.3:a:fortinet:fortiweb:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
34.98%
Probability of exploitation in next 30 days
EPSS Percentile
98.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.3498 is in the 95th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

fortinetvendor investigatingvia nvd_reference
View patch

References

fortiguard.com / psirt/FG-IR-21-186
Vendor Advisory