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F5 BIG-IP and BIG-IQ CVE-2026-41959

| EUVDEUVD-2026-29992 HIGH
Incorrect Permission Assignment for Critical Resource (CWE-732)
2026-05-13 f5 GHSA-qxf3-7mw3-hq68
7.1
CVSS 4.0 · Vendor: f5
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Attack ChainAIDerived

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

  1. Access
    Obtain valid credentials
  2. Delivery
    Authenticate to BIG-IP/BIG-IQ
  3. Exploit
    Query iControl REST or tmsh diagnostics
  4. Execution
    Extract network topology
  5. Persist
    Identify backend systems
  6. Impact
    Enumerate target infrastructure

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V13 - Configuration Permission assignment review
Exploitation Conditions

Attacker must possess valid, authenticated credentials for BIG-IP or BIG-IQ (PR:L in CVSS vector). The tmsh network diagnostics commands and iControl REST diagnostics/monitoring endpoints must be accessible from the network (AV:N in CVSS vector indicates no local access required). No special configuration or non-default deployment mode is explicitly described; the vulnerability affects standard deployments where network diagnostics are enabled. The impact is limited to information disclosure (C:H/I:N/A:N); no modifications to system state or availability impact are possible via this vector alone.

Impact

The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N) indicates this is a remotely exploitable, low-complexity attack requiring low-level authentication with high confidentiality impact. While no KEV status or active exploitation data is provided, the requirement for prior authentication (PR:L) significantly reduces real-world risk compared to unauthenticated exploits, as it presupposes an attacker has already obtained valid credentials. However, the high confidentiality rating (C:H) paired with no integrity or availability impact suggests this is specifically a reconnaissance/information gathering vulnerability that could enable further attacks. EPSS data is absent; without exploitation probability metrics, reliance falls on CVSS scoring and the authenticated requirement as the primary risk moderators. Organizations should prioritize based on the sensitivity of network topology data in their environment and the number of users with authenticated access.

Exploit ScenarioDerived

A contractor with basic user credentials (e.g., read-only monitoring access) authenticates to the BIG-IP iControl REST API and queries the network diagnostics endpoints, discovering the internal IP addresses, DNS names, and connection status of backend servers that should be restricted to administrators only. The attacker exports this network topology data to map internal infrastructure, then uses it to plan targeted attacks against discovered backend systems.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – May 13, 2026

Incorrect permission assignment in BIG-IP and BIG-IQ TMOS Shell (tmsh) network diagnostics commands and iControl REST allows authenticated attackers to view network status of destination systems. Affected versions vary by product line; vendor has released patches. Authentication is required, limiting exposure to users with valid credentials, but the high confidentiality impact (CVSS 6.5) makes this a material information disclosure risk for organizations managing sensitive network infrastructure.

RemediationAI

Apply vendor-released patch from F5 as documented in https://my.f5.com/manage/s/article/K000161022. Exact patched versions are not enumerated in available data; consult the F5 advisory to identify the correct upgrade path for your specific BIG-IP or BIG-IQ version and product line. As an interim control, restrict API access to tmsh network diagnostics commands and iControl REST endpoints to trusted administrative subnets or restrict them at the load balancer/firewall level. Additionally, implement role-based access control (RBAC) enforcement in F5 console settings to ensure only administrators requiring network diagnostics access are granted those permissions, though this does not address the underlying permission assignment bug. Monitor authentication logs for suspicious access patterns to tmsh and iControl REST by low-privilege accounts.

Affected VersionsENISA

BIG-IP 21.0.0 <21.0.0.2
BIG-IQ 8.4.0 <*
BIG-IP 16.1.0 <*
BIG-IP 17.5.0 <17.5.1.6
BIG-IP 17.1.0 <17.1.3.2

Affected Packages

euvd big_ip fix: 17.1.3.2, 17.5.1.6, 21.0.0.2

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

The vulnerability stems from improper access control enforcement (CWE-732) in two distinct F5 components: the TMOS Shell (tmsh) command-line interface used for system administration and diagnostics, and the iControl REST API which provides programmatic access to BIG-IP/BIG-IQ configuration and monitoring. The tmsh network diagnostics commands and iControl REST endpoints fail to properly validate that the authenticated user has the required permissions to view network status information, allowing privilege escalation or lateral access to sensitive network topology and status data that should be restricted by role-based access control policies.

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Severity by source

Vendor (f5) PRIMARY 7.1 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (f5) · only source for this CVE.

CVSS VectorVendor: f5

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
Low
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
None
Vulnerable system: Availability
None
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

3
Severity Changed
May 13, 2026 - 16:22 NVD
MEDIUM HIGH
CVSS changed
May 13, 2026 - 16:22 NVD
6.5 (MEDIUM) 7.1 (HIGH)
CVE Published
May 13, 2026 - 14:12 nvd
MEDIUM 6.5

DescriptionCVE.org

Incorrect permission assignment vulnerabilities exist in BIG-IP and BIG-IQ TMOS Shell (tmsh) network diagnostics commands and in BIG-IP iControl REST. These vulnerabilities may allow an authenticated attacker to view the network status of destination systems.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Threat Intelligence Overview

EPSS Score
0.0%
Top 88% exploitable
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 HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

36
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +36
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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