CVE-2025-21815 mm/compaction: fix UBSAN shift-out-of-bounds warning

What is CVE-2025-21815?

CVE-2025-21815 is a high-severity vulnerability in Linux kernel, published on 27 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

mm/compaction: fix UBSAN shift-out-of-bounds warning

syzkaller reported a UBSAN shift-out-of-bounds warning of (1UL << order) in isolate_freepages_block(). The bogus compound_order can be any value because it is union with flags. Add back the MAX_PAGE_ORDER check to fix the warning.

Weakness: CWE-125

Which versions are affected by CVE-2025-21815?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21815?

Apply the vendor's patch.

Is CVE-2025-21815 being exploited?

There is no known exploitation of CVE-2025-21815 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 BELL-CVE-2025-21815, DEBIAN-CVE-2025-21815, GHSA-37p3-cfcq-p2hp, ROOT-OS-UBUNTU-2404-CVE-2025-21815, UBUNTU-CVE-2025-21815.