Security readout for executives and security teams
Plain-English summary
CVE-2021-25741 is a Kubernetes flaw where a user able to create a container with subPath volume mounts could reach files outside the intended volume, including host filesystem data. For businesses, the concern is tenant or workload isolation failure inside affected clusters.
Executive priority
Treat as high priority for shared, multi-tenant, or CI-driven Kubernetes environments. Prioritize confirming affected cluster versions and applying vendor guidance because successful abuse could undermine node-level file isolation.
Technical view
Kubernetes subPath volume mount handling could be bypassed through a symlink exchange, allowing access outside the mounted volume. The CVSS 3.1 score is 8.8 high, with low complexity, low privileges required, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most relevant to Kubernetes clusters where users, service accounts, CI systems, or tenants can create or modify Pods using subPath volume mounts. The source bundle does not specify affected version ranges.
Exploitation context
The bundle does not cite active exploitation, and KEV status is false. Exploitation requires some Kubernetes privilege to create a container, but no user interaction is indicated by the CVSS vector.
Researcher notes
Evidence supports a Kubernetes subPath symlink exchange issue with host filesystem access impact. The provided bundle lacks exact fixed versions, affected version ranges, proof of exploitation, and detailed mitigations, so remediation should defer to the Kubernetes advisory and vendor notices.
Mitigation direction
- Review Kubernetes advisory and GitHub issue for fixed version guidance.
- Upgrade Kubernetes components according to vendor-published remediation instructions.
- Inventory workloads using subPath volume mounts.
- Restrict who can create or modify Pods in affected clusters.
- Check downstream vendor advisories, including NetApp if applicable.
Validation and detection
- Identify clusters and distributions potentially covered by the Kubernetes advisory.
- Search workload manifests for subPath volume mount usage.
- Review RBAC for principals allowed to create or update Pods.
- Confirm remediation against the Kubernetes security announcement and issue.
- Check host access monitoring for unexpected volume boundary violations.
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-20: Exact CWE lookup
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Open ATT&CK lookupContainer behavior lookup
The affected technology mentions containers, so container-specific ATT&CK technique review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-25741 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
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/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.
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:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://groups.google.com/g/kubernetes-security-announce/c/nyfdhK24H7sCVE reference · x_refsource_MISC
- https://github.com/kubernetes/kubernetes/issues/104980CVE reference · x_refsource_MISC
- https://security.netapp.com/advisory/ntap-20211008-0006/CVE reference · x_refsource_CONFIRM
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 Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.