What’s Vulnerable › Vulnerabilities

CVE-2025-21993: iscsi_ibft: Fix UBSAN shift-out-of-bounds warning in ibft_attr_show_nic()

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-02 · updated 2026-06-17
• Weakness: CWE-125

Description

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

• Linux kernel: before 6.1.132; from 6.2 before 6.6.84; from 6.7 before 6.12.20; from 6.13 before 6.13.8; 6.14-rc1 — fixed in 6.1.132, 6.12.20, 6.13.8, 6.6.84

How to fix

Upgrade to a fixed version: Linux kernel 6.1.132, 6.12.20, 6.13.8, 6.6.84. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/07e0d99a2f701123ad3104c0f1a1e66bce74d6e5
• https://git.kernel.org/stable/c/2d1eef248107bdf3d5a69d0fde04c30a79a7bf5d
• https://git.kernel.org/stable/c/9bfa80c8aa4e06dff55a953c3fffbfc68a3a3b1c
• https://git.kernel.org/stable/c/a858cd58dea06cf85b142673deea8c5d87f11e70
• https://git.kernel.org/stable/c/b253660fac5e0e9080d2c95e3a029e1898d49afb
• https://git.kernel.org/stable/c/b388e185bfad32bfed6a97a6817f74ca00a4318f
• https://git.kernel.org/stable/c/c1c6e527470e5eab0b2d57bd073530fbace39eab
• https://git.kernel.org/stable/c/f763c82db8166e28f45b7cc4a5398a7859665940
• https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
• https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html

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