CVE-2025-38733 | s390/mm: Do not map lowcore with identity mapping

In the Linux kernel, the following vulnerability has been resolved: s390/mm: Do not map lowcore with identity mapping Since the identity mapping is pinned to address zero the lowcore is always also mapped to address zero, this happens regardless of the relocate_lowcore command line option. If the option is specified the lowcore is mapped twice, instead of only once. This means that NULL pointer accesses will succeed instead of causing an exception (low address protection still applies, but covers only parts). To fix this never map the first two pages of physical memory with the identity mapping.

Published: 2025-09-05 Last update: 2025-11-25 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-2025-38733 is rated Low Risk (22.9/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.02%). 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-2025-38733

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 2025-09-06 — 0.02% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-38733

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/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:N)
Doesn’t really leak secrets in a meaningful 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 3.6 [email protected]

Weakness enumeration for CVE-2025-38733

OS Trackers for CVE-2025-38733

vendor priority summary link
debian unimportant CVE-2025-38733 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-2025-38733
redhat low — https://access.redhat.com/security/cve/CVE-2025-38733
suse medium CVE-2025-38733 severity moderate: SUSE including 94 source package names (cluster-md-kmp-64kb-6.12.0-160000.6.1, cluster-md-kmp-default, …), 452 product×package rows across 82 product lines (Image SLES-Azure-3P, Image SLES-Azure-Basic, … (82 product lines)): Known Not Affected 254, Fixed 177, First Fixed 21. https://www.suse.com/security/cve/CVE-2025-38733/
ubuntu medium CVE-2025-38733 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1414 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): DNE 1017, ignored 176, not-affected 128, released 88, needed 3, needs-triage 2. https://ubuntu.com/security/CVE-2025-38733

Affected software / configurations for CVE-2025-38733

Vendor Product Version Raw CPE
linux linux_kernel >= 6.10.11, < 6.11 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.11.1, < 6.12.44 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.13, < 6.16.4 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel 6.11 cpe:2.3:o:linux:linux_kernel:6.11:-:*:*:*:*:*:*
linux linux_kernel 6.11 cpe:2.3:o:linux:linux_kernel:6.11:rc5:*:*:*:*:*:*
linux linux_kernel 6.11 cpe:2.3:o:linux:linux_kernel:6.11:rc6:*:*:*:*:*:*
linux linux_kernel 6.11 cpe:2.3:o:linux:linux_kernel:6.11:rc7:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*
linux linux_kernel 6.17 cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*

References for CVE-2025-38733

cvelogic Threat Intelligence