Vulnerability Database

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Total vulnerabilities in the database

CVE-2026-45990 — linux / linux_kernel

Integer Overflow or Wraparound

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

slub: fix data loss and overflow in krealloc()

Commit 2cd8231796b5 ("mm/slub: allow to set node and align in k[v]realloc") introduced the ability to force a reallocation if the original object does not satisfy new alignment or NUMA node, even when the object is being shrunk.

This introduced two bugs in the reallocation fallback path:

  1. Data loss during NUMA migration: The jump to 'alloc_new' happens before 'ks' and 'orig_size' are initialized. As a result, the memcpy() in the 'alloc_new' block would copy 0 bytes into the new allocation.

  2. Buffer overflow during shrinking: When shrinking an object while forcing a new alignment, 'new_size' is smaller than the old size. However, the memcpy() used the old size ('orig_size ?: ks'), leading to an out-of-bounds write.

The same overflow bug exists in the kvrealloc() fallback path, where the old bucket size ksize(p) is copied into the new buffer without being bounded by the new size.

A simple reproducer:

// e.g. add to lkdtm as KREALLOC_SHRINK_OVERFLOW while (1) { void *p = kmalloc(128, GFP_KERNEL); p = krealloc_node_align(p, 64, 256, GFP_KERNEL, NUMA_NO_NODE); kfree(p); }

demonstrates the issue:

================================================================== BUG: KFENCE: out-of-bounds write in memcpy_orig+0x68/0x130

Out-of-bounds write at 0xffff8883ad757038 (120B right of kfence-#47): memcpy_orig+0x68/0x130 krealloc_node_align_noprof+0x1c8/0x340 lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm] lkdtm_do_action+0x3a/0x60 [lkdtm] ...

kfence-#47: 0xffff8883ad756fc0-0xffff8883ad756fff, size=64, cache=kmalloc-64

allocated by task 316 on cpu 7 at 97.680481s (0.021813s ago): krealloc_node_align_noprof+0x19c/0x340 lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm] lkdtm_do_action+0x3a/0x60 [lkdtm] ...

Fix it by moving the old size calculation to the top of __do_krealloc() and bounding all copy lengths by the new allocation size.

  • Published: May 27, 2026
  • Updated: Jun 17, 2026
  • CVE: CVE-2026-45990
  • Severity: Medium
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: Medium
  • Score: 5.5
  • AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWEs:

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CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

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Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

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