Security readout for executives and security teams
Plain-English summary
CVE-2021-47327 is a Linux kernel bug in ARM SMMU power-management error handling. A failed runtime resume can leave a device reference count unbalanced, risking resource leakage and possible local confidentiality or availability impact. It matters most for Linux systems using affected ARM IOMMU/SMMU code paths.
Executive priority
Prioritize remediation for affected ARM Linux fleets where local users, workloads, or tenants can execute code. The business urgency is high for shared or multi-user systems, moderate for tightly controlled appliances pending vendor confirmation.
Technical view
arm_smmu_rpm_get() used pm_runtime_get_sync(), which increments the SMMU runtime PM refcount even when returning an error. Caller error paths did not drop that reference, causing a refcount leak. Stable fixes replace it with pm_runtime_resume_and_get() to keep reference counts balanced on failure.
Likely exposure
Exposure is likely limited to Linux systems running affected kernel builds with the ARM SMMU driver in use. The source lists Linux kernel version entries including 5.0, 5.4.134, 5.10.52, 5.12.19, 5.13.4, and 5.14, but distribution backports require vendor-specific checking.
Exploitation context
The CVSS vector is local, low complexity, low privilege, and no user interaction. The source bundle says KEV is false, and no provided source states active exploitation. Treat this as a local kernel risk, not a confirmed internet-exploited issue.
Researcher notes
Evidence supports a reference-count leak in ARM SMMU runtime PM failure handling, classified as CWE-911 with CVSS 7.1. The provided sources identify stable kernel commits but do not establish exploit availability, affected distributions, or product-specific package names.
Mitigation direction
- Upgrade to a kernel containing the referenced stable fixes.
- Check Linux distribution advisories for backported fixes.
- Prioritize ARM systems using SMMU/IOMMU functionality.
- Track vendor guidance if packaged kernel status is unclear.
Validation and detection
- Inventory Linux kernel versions across ARM-based systems.
- Confirm whether the ARM SMMU driver is built or loaded.
- Map installed kernels to vendor fixed package versions.
- Review kernel changelogs for the referenced stable commits.
- Document systems needing reboot after kernel updates.
Public sources used
- CVE Program
- CVE List V5
- Linux stable commit 3761ae0d0e549f2acdaf11f49df4ed06d256b20f
- Linux stable commit c4007596fbdabc29f858dc2e1990858a146b60b2
- Linux stable commit fbf4daa6f4105e01fbd3868006f65c163365c1e3
- Linux stable commit fe92c058199067ae90cf2a901ddf3c271893557a
- Linux stable commit 1adf30f198c26539a62d761e45af72cde570413d
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-911: 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-2021-47327 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
- 7.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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
1 official scoreWe 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:N/A:H1.85.2CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
7.1HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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/3761ae0d0e549f2acdaf11f49df4ed06d256b20fCVE reference, Linux
- https://git.kernel.org/stable/c/c4007596fbdabc29f858dc2e1990858a146b60b2CVE reference, Linux
- https://git.kernel.org/stable/c/fbf4daa6f4105e01fbd3868006f65c163365c1e3CVE reference, Linux
- https://git.kernel.org/stable/c/fe92c058199067ae90cf2a901ddf3c271893557aCVE reference, Linux
- https://git.kernel.org/stable/c/1adf30f198c26539a62d761e45af72cde570413dCVE 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.
Improper Update of Reference Count
Improper Update of Reference Count represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.