CVE-2026-64368 mm/slab: do not limit zeroing to orig_size when only red zoning is enabled

What is CVE-2026-64368?

CVE-2026-64368 is a high-severity vulnerability in Linux kernel, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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

mm/slab: do not limit zeroing to orig_size when only red zoning is enabled

When init (zeroing) on allocation is requested, for kmalloc() we generally have to zero the full object size even if a smaller size is requested, in order to provide krealloc()'s __GFP_ZERO guarantees.

But if we track the requested size, krealloc() uses that information to do the right thing, so we can zero only the requested size. With red zoning also enabled, any extra size became part of the red zone, so it must not be zeroed and thus we must zero only the requested size.

However the current check is imprecise, and will trigger also when only SLAB_RED_ZONE is enabled without SLAB_STORE_USER (which enables tracking the requested size). This means enabling red zoning alone can compromise krealloc()'s __GFP_ZERO contract.

Fix this by using slub_debug_orig_size() instead, which is the exact check for whether the requested size is tracked. We don't need to care if red zoning is also enabled or not. Also update and expand the comment accordingly.

Weakness: CWE-665

Which versions are affected by CVE-2026-64368?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-64368?

Apply the vendor's patch.

Is CVE-2026-64368 being exploited?

There is no known exploitation of CVE-2026-64368 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-93467, BELL-CVE-2026-64368, DEBIAN-CVE-2026-64368, GHSA-m4hc-cp9r-f6rj, ROOT-OS-UBUNTU-2204-CVE-2026-64368, UBUNTU-CVE-2026-64368.