# CVE-2026-39458: F5 BIG-IP TMM denial of service in DNS cache profile

Source: https://junglewise.ai/threats/cve-2026-39458-f5-big-ip-tmm-denial-of-service-in-dns-cache-profile  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-13. Updated: 2026-06-29  
License: CC BY 4.0 with a link back

CVE-2026-39458 · Severity: high · CVSS 7.5 · Published 2026-05-13

F5 BIG-IP is a suite of networking devices used to manage and secure enterprise web traffic. A vulnerability in the DNS caching feature allows a remote attacker to send specific network traffic that crashes the system's core processing engine. This results in a complete service outage, preventing legitimate users from accessing applications protected or managed by the affected BIG-IP device.

Technologies: [F5 BIG-IP DNS](https://junglewise.ai/threats/technologies/big-ip-dns), [F5 Big-Ip Access Policy Manager](https://junglewise.ai/threats/technologies/big-ip-access-policy-manager), [F5 Big-Ip Advanced Firewall Manager](https://junglewise.ai/threats/technologies/big-ip-advanced-firewall-manager), [F5 Big-Ip Local Traffic Manager](https://junglewise.ai/threats/technologies/big-ip-local-traffic-manager). Vendors: [F5](https://junglewise.ai/threats/vendors/f5).

## Quick answers

**Is CVE-2026-39458 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39458 being exploited in the wild.

**How severe is CVE-2026-39458?** High severity, with a CVSS score of 7.5, published 13 May 2026.

**Which products and versions are affected?** F5 BIG-IP DNS 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0, Undisclosed (EoTS versions excluded); 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 Local Traffic Manager 16.1.0 - 16.1.6, 17.5.0 - 17.5.1, 21.0.0.

**Is there a fix for CVE-2026-39458?** 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-2026-39458 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-39458?** Check whether you run F5 BIG-IP DNS, F5 Big-Ip Access Policy Manager, F5 Big-Ip Advanced Firewall 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

A denial-of-service vulnerability exists in F5 BIG-IP when a DNS profile with DNS cache is enabled on a virtual server. The issue is rooted in an 'Access of Uninitialized Pointer' (CWE-824) within the Traffic Management Microkernel (TMM). A remote, unauthenticated attacker can send undisclosed network traffic to the virtual server, triggering a TMM crash and subsequent system restart. This affects multiple BIG-IP modules including DNS, LTM, AFM, and APM across versions 16.1.x, 17.5.x, and 21.0.0. F5 has released advisory K000160945 to address the issue.

## Affected products

- F5 BIG-IP DNS 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
- 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: advisory: Initial publication of the vulnerability advisory

## References

- [https://my.f5.com/manage/s/article/K000160945](https://my.f5.com/manage/s/article/K000160945)

## Related threats

- [F5 BIG-IP Appliance mode restriction bypass via path traversal](https://junglewise.ai/threats/cve-2026-42930-f5-big-ip-appliance-mode-restriction-bypass-via-path-traversal)
- [F5 BIG-IP privilege escalation in iControl SOAP via SNMP configuration](https://junglewise.ai/threats/cve-2026-42924-f5-big-ip-privilege-escalation-in-icontrol-soap-via-snmp)
- [F5 BIG-IP DoS in TMM via Client SSL Dynamic Record Sizing](https://junglewise.ai/threats/cve-2026-42920-f5-big-ip-dos-in-tmm-via-client-ssl-dynamic-record-sizing)
- [F5 BIG-IP privilege escalation in multiple modules](https://junglewise.ai/threats/cve-2026-42919-f5-big-ip-privilege-escalation-in-multiple-modules)
- [F5 BIG-IP DoS via HTTP/2 iRule redirection](https://junglewise.ai/threats/cve-2026-42409-f5-big-ip-dos-via-http-2-irule-redirection)