CVE-2026-42058: F5 BIG-IP information leak in iControl REST

CVE-2026-42058 · Severity: medium · CVSS 4.3 · Published 2026-05-13

A vulnerability in F5 BIG-IP networking devices could allow an authorized user to view the names of other local user accounts on the system. BIG-IP is a suite of application delivery and security services used to manage and protect corporate network traffic. While this does not allow an attacker to take over the system or access customer data directly, it provides them with valid usernames that could be used to launch more targeted password-guessing or social engineering attacks.

Technologies: F5 BIG-IP, F5 BIG-IP Advanced WAF, F5 Big-Ip Access Policy Manager, F5 Big-Ip Advanced Firewall Manager, F5 Big-Ip Local Traffic Manager. Vendors: F5.

Quick answers

Is CVE-2026-42058 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-42058 being exploited in the wild.
How severe is CVE-2026-42058?
Medium severity, with a CVSS score of 4.3, published 13 May 2026.
Which products and versions are affected?
F5 BIG-IP All versions prior to EoTS (End of Technical Support); F5 BIG-IP Advanced WAF 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0; F5 Big-Ip Access Policy Manager 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0; F5 Big-Ip Advanced Firewall Manager 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0; and 1 more.
Is there a fix for CVE-2026-42058?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-42058 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-42058?
Check whether you run F5 BIG-IP, F5 BIG-IP Advanced WAF, F5 Big-Ip Access Policy Manager or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An information disclosure vulnerability exists in the F5 BIG-IP iControl REST interface due to incorrect permission assignment for critical resources (CWE-732). An authenticated attacker with network access to the iControl REST interface can send specially crafted, undisclosed requests to reveal the names of local user accounts. This vulnerability requires low privileges (PR:L) and no user interaction. The leaked information (usernames) can be used to facilitate further reconnaissance or brute-force attacks against the management plane. The issue affects multiple BIG-IP modules including LTM, APM, and AFM across versions 16.1.x, 17.5.x, and 21.0.0.

Affected products

  • F5 BIG-IP Access Policy Manager 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0
  • F5 BIG-IP Advanced Firewall Manager 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0
  • F5 BIG-IP Advanced WAF 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0
  • F5 BIG-IP Local Traffic Manager 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0

Timeline

  • 2026-05-13: disclosed
  • 2026-05-13: advisory

References

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