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

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.

Published: 2025-02-27 Last update: 2026-06-17 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-21815 is rated Low Risk (31.2/100): CVSS High severity, with low exploitation likelihood (EPSS 0.18%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-21815

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.04% 0.18% +0.14%
2 2025-02-28 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21815

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.1 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.2 [email protected]

Weakness enumeration for CVE-2025-21815

OS Trackers for CVE-2025-21815

vendor priority summary link
debian unimportant CVE-2025-21815 unimportant priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-21815
redhat medium — https://access.redhat.com/security/cve/CVE-2025-21815
suse medium CVE-2025-21815 severity moderate: SUSE including 417 source package names (2.1.3-6.11:kernel-default-6.4.0-28.1, 2.1.3-6.12:kernel-default-base-6.4.0-28.1.21.6, …), 746 product×package rows across 133 product lines (Container suse/sl-micro/6.0/base-os-container, Container suse/sl-micro/6.0/kvm-os-container, … (133 product lines)): Fixed 361, Known Affected 231, Known Not Affected 154. https://www.suse.com/security/cve/CVE-2025-21815/
ubuntu medium CVE-2025-21815 medium priority: Ubuntu including 150 source packages (linux, linux-allwinner-5.19, …), 1487 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1097, ignored 148, released 128, not-affected 114. https://ubuntu.com/security/CVE-2025-21815

Affected software / configurations for CVE-2025-21815

Vendor Product Version Raw CPE
linux linux_kernel >= 6.7, < 6.12.14 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.13, < 6.13.3 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

References for CVE-2025-21815

cvelogic Threat Intelligence