How to fix CVE-2025-21993?

Within 7 days: Identify all affected systems and apply vendor patches promptly. Vendor patch is available.

Is Linux Kernel affected by CVE-2025-21993?

CVE-2025-21993 presents moderate security risk, a out-of-bounds read vulnerability rated CVSS 7.1. Exploitation could compromise the security of affected deployments. A patch is available and should be applied as part of regular vulnerability management.

CVE-2025-21993

HIGH

2025-04-02 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Information Disclosure Buffer Overflow Linux Linux Kernel Redhat Suse

7.1

CVSS 3.1

CVSS VectorNVD

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 28, 2026 - 18:34 vuln.today

Patch Released

Mar 28, 2026 - 18:34 nvd

Patch available

CVE Published

Apr 02, 2025 - 13:15 nvd

HIGH 7.1

DescriptionNVD

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.

AnalysisAI

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. Rated high severity (CVSS 7.1), this vulnerability is low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.

Technical ContextAI

This vulnerability is classified as Out-of-bounds Read (CWE-125), which allows attackers to read data from memory outside the intended buffer boundaries. 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. Affected products include: Linux Linux Kernel.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Validate array indices and buffer lengths. Use memory-safe languages. Enable AddressSanitizer during testing.

Vendor StatusVendor

CVE-2025-21993 vulnerability details – vuln.today

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