VulnerabilityPublished 13 May 2026Updated 2 Jul 2026

CVE-2026-42058: F5 BIG-IP · Incorrect Permissions

Affects F5 BIG-IPSource CVE Database V5

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Not known to be exploited · CVSS 4.3 Medium · fixed in 21.0.0.2 : update F5 BIG-IP when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

4.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 21.0.0.2, 17.5.1.6, 17.1.3.2

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

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade F5 BIG-IP to 21.0.0.2, 17.5.1.6 or 17.1.3.2.

Affected software

Product	Affected	Fixed in
F5BIG-IP	Affected >=21.0.0 <21.0.0.2 >=17.5.0 <17.5.1.6 >=17.1.0 <17.1.3.2 >=16.1.0	Fixed in 21.0.0.2 17.5.1.6 17.1.3.2

AI-suggested

Limit access to the iControl REST interface to trusted administrators to reduce exposure.

Description

An authenticated attacker's undisclosed requests to BIG-IP iControl REST can lead to an information leak of BIG-IP local user account names. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Impact

An authenticated attacker can obtain information about local user account names on the BIG-IP system via the iControl REST interface. This information disclosure could aid in further targeted attacks or reconnaissance but does not directly impact system integrity or availability. The confidentiality impact is limited to user account name leakage.

Summary

This vulnerability (CVE-2026-42058) in F5 BIG-IP arises from incorrect permission assignment (CWE-732) for critical resources accessed via the iControl REST interface. Authenticated attackers can send certain undisclosed requests that result in the leakage of local user account names. The issue affects multiple versions of BIG-IP, specifically 16.1.0, 17.1.0, 17.5.0, and 21.0.0. The CVSS v3.1 base score is 4.3, indicating medium severity, with the vector showing network attack vector, low attack complexity, required privileges, no user interaction, and confidentiality impact only. No official remediation or patch has been announced, and no exploits are currently known in the wild.

CWE-732Incorrect Permission Assignment for Critical Resource (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.
Implementation
When using a critical resource such as a configuration file, check to see if the resource has insecure permissions (such as being modifiable by any regular user), and generate an error or even exit the software if there is a possibility that the resource could have been modified by an unauthorized party.
Architecture and Design
Divide the software into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully defining distinct user groups, privileges, and/or roles. Map these against data, functionality, and the related resources. Then set the permissions accordingly.
Architecture and Design · Operation · Sandbox or Jail
Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.3.3 (opens in a new tab)
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Directory Indexing (opens in a new tab)
Using Malicious Files (opens in a new tab)
Exploiting Incorrectly Configured Access Control Security Levels (opens in a new tab)
Signing Malicious Code (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

my.f5.com/manage/s/article/K000160903 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 2 Jul 2026, 21:04 UTC

WeaknessesCWE-732

Technical details

References

Community reviews

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