CVE-2026-39812Network attack vector

Browser script execution via stored web input

Published Apr 14, 2026 · Updated Apr 14, 2026

Stored XSS in Fortinet FortiSandbox and FortiSandbox PaaS allows privileged attackers to execute script in another user's browser. The web interface stores values from crafted HTTP requests and later renders them without adequate output neutralization; Fortinet has not named the affected fields or pages. A highly privileged attacker must submit the payload and a separate user must open affected content; published impact is limited to browser-session confidentiality and integrity.

CVSS severity4.8
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Fortinet FortiSandbox and FortiSandbox PaaS allows privileged attackers to execute script in another user's browser. The web interface stores values from crafted HTTP requests and later renders them without adequate output neutralization; Fortinet has not named the affected fields or pages. A highly privileged attacker must submit the payload and a separate user must open affected content; published impact is limited to browser-session confidentiality and integrity.

The record

CVE
CVE-2026-39812
Published
Apr 14, 2026
Updated
Apr 14, 2026
Vendor
Fortinet
Product
FortiSandbox
Classifications
CWE-79, T1189
Attack vector
network
Privileges
authenticated

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

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Is a vulnerable build present?

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

  1. Affected versionversion=4.2.1 <=4.2.8
  2. Affected versionversion=4.4.0 <=4.4.8
  3. Affected versionversion=5.0.0 <=5.0.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Fortinet · FortiSandboxversion=4.2.1 <=4.2.8; version=4.4.0 <=4.4.8; version=5.0.0 <=5.0.4
Fortinet · FortiSandbox PaaSversion=4.2.1 <=4.2.8; version=4.4.0 <=4.4.8; version=5.0.0 <=5.0.5

Published CVSS scores

4.8Fortinet, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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

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Your stack

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