Out-of-bounds Read in Linux

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.

Vulnerability class: Buffer Overflow

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H.

EPSS exploit prediction

EPSS: 0.002 (10.7th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 11th percentile — 10.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2025-21993: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.000

Affected products

  • Linux — versions 138fe4e069798d9aa948a5402ff15e58f483ee4e, 2.6.26, 0
  • Linux Kernel — versions 6.14

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2025-21993?
CVE-2025-21993 is a high-severity vulnerability in Linux, classified under Out-of-bounds Read. CVSS score: 7.1/10. Published 2025-04-02.
How severe is CVE-2025-21993?
High severity. CVSS v3 base score is 7.1 out of 10.
Is CVE-2025-21993 known to be exploited?
4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.