CVE intelligence

CVE-2025-21993

Vulnerability intelligence

Published Apr 2, 2025Sources checked Oct 9, 2026

7.1HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2025-21993 and is rated High severity with a CVSS score of 7.1. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Aug 12, 2026

CBL-Mariner Releases

Vendor-listed releases

5.15.180.1-1
6.6.85.1-2

CISA KEVNot listedBased on the latest collected catalog

EPSS0.2%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2025-21993?

In the Linux kernel, the following vulnerability has been resolved:

iscsi_ibft: Fix UBSAN shift-out-of-bounds warning in ibft_attr_show_nic()

When performing an iSCSI boot using IPv6, iscsistart still reads the /sys/firmware/ibft/ethernetX/subnet-mask entry. Since the IPv6 prefix length is 64, this causes the shift exponent to become negative, triggering a UBSAN warning.

As the concept of a subnet mask does not apply to IPv6, the value is set to ~0 to suppress the warning message.

Source: NVD