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Fortinet FortiWeb EUVDEUVD-2026-57193

| CVE-2026-26035 CRITICAL
Improper Authentication (CWE-287)
2026-08-12 fortinet GHSA-q9j3-5j7m-6w3x
9.8
CVSS 3.1 · Vendor: fortinet
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Reach FortiWeb GUI/CLI over network
  2. Delivery
    Submit login with random credentials
  3. Exploit
    Auth check improperly accepts them
  4. Execution
    Obtain admin session
  5. Persist
    Modify WAF policy or exfiltrate config
  6. Impact
    Full appliance compromise

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V6 - Authentication Authentication mechanism validation
MITRE ATT&CK

2 techniques across 2 tactics: Defense Evasion, Initial Access

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

The attacker needs network reachability to the FortiWeb administrative GUI or CLI (the management interface) on a vulnerable build (7.0.0-7.0.12, 7.2.0-7.2.12, 7.4.0-7.4.11, 7.6.0-7.6.6, or 8.0.0-8.0.2); no valid account, no user interaction, and no prior foothold are required, and default configurations are affected because the flaw sits in the credential-verification path itself. The primary limiting factor is exposure of the management interface: deployments that restrict admin GUI/CLI access to a trusted management network or specific trusthosts are not remotely exploitable by arbitrary internet attackers, sharply reducing real-world reach despite the 9.8 base score.

Impact

This is a genuine top-priority issue, not a paper-tiger high CVSS. The CVSS 3.1 vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H describes a fully remote (AV:N), low-complexity (AC:L), unauthenticated (PR:N), no-interaction (UI:N) attack yielding total confidentiality, integrity, and availability impact - the maximum realistic base score of 9.8. No EPSS score or SSVC decision was provided in the input, and the CVE is not currently on CISA KEV, so exploitation probability cannot be quantified from the data given; however, an unauthenticated admin-login bypass on an internet-facing security appliance is exactly the profile that historically attracts rapid exploitation. The vector is internally consistent with the description (remote, unauthenticated, full admin), so there is no conflicting signal to reconcile. Absence of a POC and KEV entry lowers the immediate certainty of active attack but does NOT lower the intrinsic severity - treat as emergency-patch priority for any internet-exposed management interface.

Exploit ScenarioDerived

An attacker locates an internet-reachable FortiWeb management GUI or CLI, submits a login request with any arbitrary username and password, and is granted an authenticated administrative session without possessing valid credentials. From that admin session they can alter WAF policies to expose or attack protected web applications, exfiltrate configuration and secrets, or disable protections. No public exploit was identified at time of analysis, but the attack requires no tooling beyond a normal login request.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.5% exploitation probability (EPSS)

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AnalysisAIv2 – Aug 12, 2026

Authentication bypass in Fortinet FortiWeb (versions 7.0.0-7.0.12, 7.2.0-7.2.12, 7.4.0-7.4.11, 7.6.0-7.6.6, and 8.0.0-8.0.2) lets a remote unauthenticated attacker log into the GUI/CLI management interface using an arbitrary, made-up username and password, granting full administrative control of the web application firewall. Tracked as CVE-2026-26035 (EUVD-2026-57193) and rated CVSS 9.8, this is an improper-authentication (CWE-287) flaw reported by Fortinet's own PSIRT (FG-IR-26-158). There is no public exploit identified at time of analysis and it is not on the CISA KEV list, but the trivial exploitability and network exposure make it a high-priority patch.

Earlier versions of this analysis (1)
v1 Aug 12, 2026 - 13:17 CVSS 8.8

Authentication bypass in Fortinet FortiWeb exposes the management GUI and CLI to remote unauthenticated attackers across five major version branches (7.0 through 8.0), allowing login with arbitrary credentials due to improper authentication logic (CWE-287). An attacker who reaches the management plane gains full administrative control over the WAF, with complete confidentiality, integrity, and availability impact. A proof-of-concept exists (CVSS E:P) and an official fix is available (RL:O); active exploitation has not been confirmed in CISA KEV at time of analysis.

RemediationAI

Upgrade to a Fortinet-patched FortiWeb release as directed in advisory FG-IR-26-158 (https://fortiguard.fortinet.com/psirt/FG-IR-26-158); the advisory lists the fixed build for each affected train (upgrade past the highest vulnerable version in your branch, e.g. beyond 8.0.2, 7.6.6, 7.4.11, 7.2.12, or 7.0.12 - confirm the exact target build in the advisory rather than assuming). Because exploitation targets the management GUI/CLI, the most effective compensating control until patched is to remove the administrative interface from any untrusted network: restrict HTTP/HTTPS/SSH admin access to a dedicated management VLAN or trusted admin hosts via local-in/trusthost policies, and disable administrative access on internet-facing interfaces entirely. Trade-off: locking down trusthosts or the management interface can break remote administration and any external monitoring that touches the management plane, so stage a management jump host or VPN before applying these restrictions.

Affected VersionsENISA

FortiWeb 8.0.0 ≤8.0.2
FortiWeb 7.4.0 ≤7.4.11
FortiWeb 7.0.0 ≤7.0.12
FortiWeb 7.2.0 ≤7.2.12
FortiWeb 7.6.0 ≤7.6.6

Affected Packages

euvd fortiweb no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

FortiWeb is Fortinet's dedicated web application firewall (WAF) appliance, deployed as a physical or virtual gateway that inspects and protects HTTP/HTTPS traffic; the affected asset per CPE is cpe:2.3:a:fortinet:fortiweb across all versions. The vulnerability class is CWE-287 (Improper Authentication): the administrative authentication logic for the management GUI and CLI fails to correctly validate supplied credentials, so any random username/password pair is accepted rather than being checked against the real credential store. This is a logic/verification failure in the auth routine itself (not a memory-safety bug), which is why it requires no valid account, no user interaction, and no special privileges to abuse.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (fortinet) PRIMARY 9.8 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 9.8 CRITICAL

Remote unauthenticated login bypass over the network with no interaction grants full admin control, so AV:N/AC:L/PR:N/UI:N and C:H/I:H/A:H; scope unchanged as impact stays within the appliance.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (fortinet).

CVSS VectorVendor: fortinet

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Updated
Aug 12, 2026 - 13:28 vuln.today
v2 - CVSS changed
Severity Changed
Aug 12, 2026 - 13:22 NVD
HIGH CRITICAL
CVSS changed
Aug 12, 2026 - 13:22 NVD
8.8 (HIGH) 9.8 (CRITICAL)
CVE Published
Aug 12, 2026 - 12:19 cve.org
HIGH 8.8

DescriptionCVE.org

An Improper Authentication vulnerability [CWE-287] vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.2, FortiWeb 7.6.0 through 7.6.6, FortiWeb 7.4.0 through 7.4.11, FortiWeb 7.2.0 through 7.2.12, FortiWeb 7.0.0 through 7.0.12 may allow a remote unauthenticated attacker to login into the Fortiweb GUI/CLI with a random username and password

Executive ViewAI

Why It Matters

Fortinet FortiWeb versions 7.0 through 8.0 contain a critical authentication bypass (CVE-2026-26035, CVSS 9.8) that allows unauthenticated attackers to gain full administrative access to WAF management interfaces, potentially compromising all protected applications and dependent systems. With no vendor-released patch identified at time of analysis, this vulnerability poses immediate risk to web application security posture and demands urgent compensating controls.

Business Impact: Severe
Compensating Controls

Network-based access controls restricting management interfaces to authorized administrative VLAN or bastion hosts only; mandatory credential rotation to unpredictable, high-entropy passwords; multi-factor authentication enforcement; continuous monitoring and alerting for authentication anomalies; optional air-gapped or offline management for critical instances; and active monitoring of Fortinet PSIRT advisories for patch release timeline.

Threat Intelligence Overview

EPSS Score
0.5%
Top 59% exploitable
Prevalence
High
widely deployed enterprise Fortinet WAF appliance
Threat Intel
1
1 sources
Social Media
1
Sightings
Data Quality
6 sources
Confidence: High

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.5%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Out-of-Cycle
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
Very High
Technical Impact
Total

Priority Score

50
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

CVE-2025-64446 CRITICAL POC
9.8 Nov 14

Fortinet FortiWeb contains a relative path traversal allowing unauthenticated attackers to execute administrative comman

CVE-2025-58034 HIGH POC
7.2 Nov 18

Fortinet FortiWeb contains an authenticated OS command injection allowing privilege escalation to execute unauthorized c

CVE-2025-52970 HIGH POC
8.1 Aug 12

A improper handling of parameters in Fortinet FortiWeb versions 7.6.3 and below, versions 7.4.7 and below, versions 7.2.

CVE-2024-48884 CRITICAL
9.1 Jan 14

Arbitrary file write and folder deletion in Fortinet FortiManager, FortiOS, and FortiProxy is possible via a path traver

CVE-2023-25610 CRITICAL
9.8 Mar 24

A buffer underwrite ('buffer underflow') vulnerability in the administrative interface of Fortinet FortiOS version 7.2.0

CVE-2021-22122 MEDIUM POC
6.1 Feb 08

An improper neutralization of input during web page generation in FortiWeb GUI interface 6.3.0 through 6.3.7 and version

CVE-2025-59719 CRITICAL
9.8 Dec 09

Authentication bypass in Fortinet FortiWeb 8.0.0, 7.6.0-7.6.4, and 7.4.0-7.4.9 allows unauthenticated remote attackers t

CVE-2021-41025 CRITICAL
9.8 Dec 08

Multiple vulnerabilities in the authentication mechanism of confd in FortiWeb versions 6.4.1, 6.4.0, 6.3.0 through 6.3.1

CVE-2021-36186 CRITICAL
9.8 Nov 02

A stack-based buffer overflow in Fortinet FortiWeb version 6.4.0, version 6.3.15 and below, 6.2.5 and below allows attac

CVE-2024-48885 CRITICAL
9.1 Jan 16

Privilege escalation via path traversal affects multiple Fortinet appliances - FortiWeb (6.4, 7.0, 7.2, 7.4.0-7.4.4, 7.6

CVE-2016-4066 HIGH
8.8 Jul 13

Cross-site request forgery (CSRF) vulnerability in Fortinet FortiWeb before 5.5.3 allows remote attackers to hijack the

CVE-2024-23665 HIGH
8.8 Jun 03

Multiple improper authorization vulnerabilities [CWE-285] in FortiWeb version 7.4.2 and below, version 7.2.7 and below,

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