CyberSecBulletin
CVE-2026-40061NVD status: Analyzed

BIG-IP: Improper Neutralization of Special Elements used in a Command

Published Updated By the CyberSecBulletin desk

CVE-2026-40061 is a high-severity improper neutralization of special elements used in a command vulnerability in BIG-IP from F5, with a CVSS 3.1 base score of 8.7 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, 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 0.24% 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.

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 Domain Name System16.1.0 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
HighAdministrator-level access is required first.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

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

Scoring systemScoreSeverityScored by
CVSS 4.08.5HighCNA (f5.com)
CVSS 3.18.7HighCNA (f5.com)

Official description

When BIG-IP DNS is provisioned, a vulnerability exists in an undisclosed iControl REST and BIG-IP TMOS Shell (tmsh) command that may allow an authenticated attacker with the Resource Administrator or Administrator role to execute arbitrary system commands with higher privileges. In Appliance mode deployments, a successful exploit can allow the attacker to cross a security boundary. 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: Improper Neutralization of Special Elements used in a Command

The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

How developers prevent this class of flaw

  • If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • If possible, ensure that all external commands called from the program are statically created.
  • Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.

More Improper Neutralization of Special Elements used in a Command vulnerabilities (CWE-77)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in BIG-IP

All BIG-IP vulnerabilities

Recent Improper Neutralization of Special Elements used in a Command vulnerabilities

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