CyberSecBulletin
CVE-2026-40060NVD status: Analyzed

BIG-IP: Unchecked Return Value

Published Updated By the CyberSecBulletin desk

CVE-2026-40060 is a high-severity unchecked return value 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 0.32% 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. Read the advisory on my.f5.com for workarounds and exact fixed builds.
  3. 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 Application Security Manager16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 21.0.0Not stated
F5Big-ip Advanced Web Application Firewall16.1.0 through 16.1.6; 17.1.0 through 17.1.3; 17.5.0 through 17.5.1; 21.0.0Not stated

Version data comes from the organisation that assigned the CVE. 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 a BIG-IP Advanced WAF or ASM security policy is configured on a virtual server, undisclosed requests can cause the bd 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: Unchecked Return Value

The product does not check the return value from a method or function.

How developers prevent this class of flaw

  • Check the results of all functions that return a value and verify that the value is expected.
  • 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.
  • Ensure that you account for all possible return values from the function.

More Unchecked Return Value vulnerabilities (CWE-252)

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 Unchecked Return Value vulnerabilities

Spotted an error? Tell us.