CyberSecBulletin
CVE-2026-42409NVD status: Analyzed

BIG-IP: NULL Pointer Dereference

Published Updated By the CyberSecBulletin desk

CVE-2026-42409 is a high-severity NULL pointer dereference vulnerability in BIG-IP from F5, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 21.0.0.1, 17.5.1.4, 17.1.3.1 as the first without the flaw, so updating BIG-IP to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.26% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update BIG-IP to 21.0.0.1 or 17.5.1.4 or 17.1.3.1, whichever matches your release line, or a later version.
  2. Update BIG-IP Next SPK to 2.0.3 or 1.7.17, whichever matches your release line, or a later version.
  3. Update BIG-IP Next CNF to 2.0.3 or 1.4.1, whichever matches your release line, or a later version.
  4. Read the advisory on my.f5.com for workarounds and exact fixed builds.
  5. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
F5BIG-IP21.0.0 up to, but not including, 21.0.0.1; 17.5.0 up to, but not including, 17.5.1.4; 17.1.0 up to, but not including, 17.1.3.1; 16.1.0 and later21.0.0.1, 17.5.1.4, 17.1.3.1
F5BIG-IP Next SPK2.0.0 up to, but not including, 2.0.3; 1.7.0 up to, but not including, 1.7.172.0.3, 1.7.17
F5BIG-IP Next CNF2.0.0 up to, but not including, 2.0.3; 1.4.0 up to, but not including, 1.4.12.0.3, 1.4.1
F5BIG-IP Next for Kubernetes2.0.0 up to, but not including, 2.1.12.1.1
F5Big-ip Next Cloud-native Network Functions1.1.0 through 1.4.0; 2.0.0 through 2.0.2Not stated
F5Big-ip Access Policy Manager21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Advanced Firewall Manager21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Advanced Web Application Firewall21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Analytics21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Application Acceleration Manager21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Application Security Manager21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Application Visibility And Reporting21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Automation Toolchain21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Carrier-grade Nat21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Container Ingress Services21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Ddos Hybrid Defender21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Domain Name System21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Edge Gateway21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Fraud Protection Service21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Global Traffic Manager21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Link Controller21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Local Traffic Manager21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Policy Enforcement Manager21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip SSL Orchestrator21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated
F5Big-ip Webaccelerator21.0.0; 16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1Not stated

Version data comes from the organisation that assigned the CVE; 1 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (f5.com).

Scoring systemScoreSeverityScored by
CVSS 4.08.7HighCNA (f5.com)
CVSS 3.17.5HighCNA (f5.com)

Official description

When an HTTP/2 profile and an iRule containing the HTTP::redirect or HTTP::respond command are configured on a virtual server, undisclosed requests can cause the Traffic Management Microkernel (TMM) process to terminate. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: NULL Pointer Dereference

The product dereferences a pointer that it expects to be valid but is NULL.

How developers prevent this class of flaw

  • For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
  • Select a programming language that is not susceptible to these issues.
  • Check the results of all functions that return a value and verify that the value is non-null before acting upon it.

More NULL Pointer Dereference vulnerabilities (CWE-476)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in BIG-IP

All BIG-IP vulnerabilities

Recent NULL Pointer Dereference vulnerabilities

Spotted an error? Tell us.