Security readout for executives and security teams
Plain-English summary
A local Linux user can trigger a race in memory movement and swap handling, potentially crashing the kernel or compromising memory integrity. The issue requires access to the affected userfaultfd functionality; it is not described as remotely exploitable.
Executive priority
Treat as a high-priority local privilege boundary and availability risk. Accelerate patching on systems allowing untrusted local users or workloads. Internet-facing status alone does not determine exposure because the vulnerable path is locally reachable.
Technical view
userfaultfd_move can relocate a swap PTE while its folio remains in swapcache without updating the folio index. A later swap fault detects inconsistent VMA addressing, causing a kernel BUG when KSM is disabled or a warning and incorrect reverse mapping when KSM is enabled.
Likely exposure
Exposure is limited to Linux systems running affected kernel lines, including versions identified from 6.8 through affected 6.12, 6.13, and 6.14 builds, where a local low-privileged user can access the relevant userfaultfd operation. Distribution backports may change exact exposure.
Exploitation context
The CVSS assessment is 7.8 with local access and low privileges required. The supplied sources do not report active exploitation, and the CVE is not listed as KEV. Practical exploitation evidence is incomplete; the documented outcomes include kernel failure and incorrect memory mapping.
Researcher notes
This is a CWE-362 race involving swapcache lifetime, moved swap PTEs, and stale folio indices. Behavior depends on KSM: disabled configurations can hit a BUG, while enabled configurations can retain incorrect reverse mappings. Exact affected distribution builds require vendor-specific verification because kernel fixes are commonly backported.
Mitigation direction
- Install a vendor-supported kernel containing the referenced stable fix.
- Reboot affected systems so the patched kernel becomes active.
- Prioritize shared, multi-user, container-hosting, and other untrusted-workload systems.
- If immediate patching is impossible, consult distribution guidance for supported userfaultfd restrictions.
Validation and detection
- Record the running kernel version and distribution package release.
- Confirm the active kernel contains a vendor backport or referenced stable fix.
- Review kernel logs for related rmap BUG, warning, or swap-fault events.
- Verify patched hosts were rebooted and are not still running the previous kernel.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-362: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2025-21984 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H13.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Base CVSS 3.1 score
4.7MediumVector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/4e9507246298fd6f1ca7bb42ef01a6e34fb93684CVE reference, Linux
- https://git.kernel.org/stable/c/b1e11bd86c0943bb7624efebdc384340a50ad683CVE reference, Linux
- https://git.kernel.org/stable/c/c50f8e6053b0503375c2975bf47f182445aebb4cCVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.