CVE-2026-63950: Software Security Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-9fqf-4mvh-6fx9
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CVSS 7.8
Published
Advisory Summary

CVE-2026-63950 is a HIGH (CVSS 7.8) security vulnerability vulnerability (General Security Weakness) affecting Software libraries in the Maven ecosystem. Remediation is available in the latest vendor maintenance releases.

CVE-2026-63950 at a Glance

CVE Identifier CVE-2026-63950
GHSA Identifier GHSA-9fqf-4mvh-6fx9
Severity HIGH
CVSS v3.1 Base Score 7.8
CWE Classification General Security Weakness
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-63950

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-63950, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under General Security Weakness. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

In the Linux kernel, the following vulnerability has been resolved: mm/rmap: initialize nr_pages to 1 at loop start in try_to_unmap_one Initialize nr_pages to 1 at the start of each loop iteration, like folio_referenced_one() does. Without this, nr_pages computed by a previous folio_unmap_pte_batch() call can be reused on a later iteration that does not run folio_unmap_pte_batch() again. mmap a 64K large folio with MAP_ANONYMOUS | MAP_DROPPABLE, then call madvise(MADV_FREE), then make the last page device-exclusive via HMM_DMIRROR_EXCLUSIVE. Trigger node reclaim through sysfs. Now, in try_to_unmap_one(), we will first clear the first 15 out of 16 entries mapping the lazyfree folio. This will set nr_pages to 15. In the next pvmw walk, this nr_pages gets reused on a device-exclusive pte, thus potentially corrupting folio refcount/mapcount. At the moment, I have a userspace program which can make the kernel spit out a trace, but the blow up is in folio_referenced_one(), because there are existing bugs in the interaction between device-private and rmap (which too I am investigating). I did a one liner kernel change to avoid going into folio_referenced_one(), and the kernel blows up at folio_remove_rmap_ptes in try_to_unmap_one which is what I wanted. Note that the bug is there not since file folio batching but lazyfree folio batching, since device-exclusive only works for anonymous folios. Userspace visible effect is simply kernel crashing somewhere due to refcount/mapcount corruption.

References

NVD — CVE-2026-63950 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-63950
git.kernel.org/stable/c/0fcc34d0d8... WEB
https://git.kernel.org/stable/c/0fcc34d0d8fefca4fea349e45c10e3a3d90350eb
git.kernel.org/stable/c/3f8968e9cb... WEB
https://git.kernel.org/stable/c/3f8968e9cbf95d5d87d32218906cab0b9b9eddbe
git.kernel.org/stable/c/f611db9b77... WEB
https://git.kernel.org/stable/c/f611db9b771b2b6775357555d2517af044fca4f0

Frequently Asked Questions

What is CVE-2026-63950?
CVE-2026-63950 is a security vulnerability in Software classified as a security vulnerability vulnerability under General Security Weakness.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-63950?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-63950?
CVE-2026-63950 has a CVSS v3.1 base score of 7.8 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-63950?
CVE-2026-63950 is classified under General Security Weakness.
How can I check Maven dependencies for CVE-2026-63950?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9fqf-4mvh-6fx9",
  "modified" : "2026-07-20T15:31:53Z",
  "published" : "2026-07-19T18:31:47Z",
  "aliases" : [ "CVE-2026-63950" ],
  "details" : "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/rmap: initialize nr_pages to 1 at loop start in try_to_unmap_one\n\nInitialize nr_pages to 1 at the start of each loop iteration, like\nfolio_referenced_one() does.\n\nWithout this, nr_pages computed by a previous folio_unmap_pte_batch() call\ncan be reused on a later iteration that does not run\nfolio_unmap_pte_batch() again.\n\nmmap a 64K large folio with MAP_ANONYMOUS | MAP_DROPPABLE, then call\nmadvise(MADV_FREE), then make the last page device-exclusive via\nHMM_DMIRROR_EXCLUSIVE.\n\nTrigger node reclaim through sysfs.  Now, in try_to_unmap_one(), we will\nfirst clear the first 15 out of 16 entries mapping the lazyfree folio. \nThis will set nr_pages to 15.  In the next pvmw walk, this nr_pages gets\nreused on a device-exclusive pte, thus potentially corrupting folio\nrefcount/mapcount.\n\nAt the moment, I have a userspace program which can make the kernel spit\nout a trace, but the blow up is in folio_referenced_one(), because there\nare existing bugs in the interaction between device-private and rmap\n(which too I am investigating).  I did a one liner kernel change to avoid\ngoing into folio_referenced_one(), and the kernel blows up at\nfolio_remove_rmap_ptes in try_to_unmap_one which is what I wanted.\n\nNote that the bug is there not since file folio batching but lazyfree\nfolio batching, since device-exclusive only works for anonymous folios.\n\nUserspace visible effect is simply kernel crashing somewhere due to\nrefcount/mapcount corruption.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-63950"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/0fcc34d0d8fefca4fea349e45c10e3a3d90350eb"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/3f8968e9cbf95d5d87d32218906cab0b9b9eddbe"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/f611db9b771b2b6775357555d2517af044fca4f0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-07-19T16:17:13Z"
  }
}