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CVE Record

CVE-2025-21745: blk-cgroup: Fix class @block_class's subsystem refcount leakage

In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: Fix class @block_class's subsystem refcount leakage blkcg_fill_root_iostats() iterates over @block_class's devices by class_dev_iter_(init|next)(), but does not end iterating with class_dev_iter_exit(), so causes the class's subsystem refcount leakage. Fix by ending the iterating with class_dev_iter_exit().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This CVE is a Linux kernel bug in block cgroup accounting. The source says an iterator was not closed, leaking a subsystem reference count. Business urgency depends on where affected kernels are deployed; no CVSS score, impact description, or active exploitation evidence is provided.

Executive priority

Handle through normal kernel patch governance unless affected systems are highly exposed or operationally sensitive. The evidence supports remediation tracking, not emergency response, because severity and exploitation status are not established.

Technical view

blkcg_fill_root_iostats() iterates block_class devices with class_dev_iter_init/next but omitted class_dev_iter_exit(), causing class subsystem refcount leakage. Kernel stable commits fix the iterator cleanup. The bundle does not state attacker prerequisites, reachable interfaces, or concrete confidentiality, integrity, or availability impact.

Likely exposure

Exposure is likely limited to systems running affected Linux kernel versions or downstream products using those kernels. Debian LTS and Siemens advisories indicate downstream tracking, but exact exposure requires matching deployed kernel packages or vendor firmware against advisory fixed versions.

Exploitation context

No active exploitation is supported by the bundle. KEV is false, and the cited sources do not describe public exploitation, exploit code, or weaponized abuse. Treat exploitability as unproven from available evidence.

Researcher notes

The root issue is a missing iterator exit call causing refcount leakage in blk-cgroup iostats handling. Source evidence is strong for the code defect and fix, but weak for security impact, triggerability, privilege requirements, and real-world exploitability.

Mitigation direction

  • Update affected Linux kernels through the distribution or product vendor channel.
  • For custom kernels, review and apply the relevant upstream stable fix.
  • Follow Debian LTS advisories for Debian-based systems.
  • Review Siemens advisories for affected Siemens products and vendor-specific fixes.
  • Monitor the CVE record for scoring or impact updates.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and embedded products.
  • Compare deployed kernels with the CVE affected version data and stable commit references.
  • Check Debian package advisory status for Debian LTS systems.
  • Check Siemens product advisories where Siemens equipment is deployed.
  • Confirm patched systems boot the expected fixed kernel.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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

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CVE-2025-21745 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

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.

0CVSS vectors
3Timeline events
2ADP providers
13Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxef45fe470e1e5410db4af87abc5d5055427945ac, ef45fe470e1e5410db4af87abc5d5055427945ac, ef45fe470e1e5410db4af87abc5d5055427945ac, ef45fe470e1e5410db4af87abc5d5055427945ac, ef45fe470e1e5410db4af87abc5d5055427945ac, ef45fe470e1e5410db4af87abc5d5055427945ac, ef45fe470e1e5410db4af87abc5d5055427945acunaffected
LinuxLinux5.9, 0, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.