CVE-2026-39811Network attack vector

Authenticated service hang via crafted HTTP requests

Published Apr 14, 2026 · Updated Apr 14, 2026

Integer overflow in cgi_buf_alloc in affected Fortinet FortiWeb releases allows remote authenticated users to cause a service hang. Crafted HTTP requests make the request-handling allocation path enter an infinite loop instead of completing or rejecting the request. Authentication with high privileges is required, and the documented consequence is loss of availability without data disclosure or modification.

CVSS severity4.9
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Integer overflow in cgi_buf_alloc in affected Fortinet FortiWeb releases allows remote authenticated users to cause a service hang. Crafted HTTP requests make the request-handling allocation path enter an infinite loop instead of completing or rejecting the request. Authentication with high privileges is required, and the documented consequence is loss of availability without data disclosure or modification.

The record

CVE
CVE-2026-39811
Published
Apr 14, 2026
Updated
Apr 14, 2026
Vendor
Fortinet
Product
FortiWeb
Classifications
CWE-190, T1499.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Apr 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=7.0.0 <=7.0.12
  2. Affected versionversion=7.2.0 <=7.2.12
  3. Affected versionversion=7.4.0 <=7.4.12
  4. Affected versionversion=7.6.0 <=7.6.6
  5. Affected versionversion=8.0.0 <=8.0.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Fortinet · FortiWebversion=7.0.0 <=7.0.12; version=7.2.0 <=7.2.12; version=7.4.0 <=7.4.12; version=7.6.0 <=7.6.6; version=8.0.0 <=8.0.3

Published CVSS scores

6.5TrendAI Zero Day InitiativeCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.9Fortinet, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo