Security readout for executives and security teams
Plain-English summary
A Linux kernel CephFS client bug can leak memory during certain authorized file-access checks. On affected systems, repeated normal-looking file access can grow kernel memory until the host reaches OOM and may hard-lock. This is primarily an availability risk, not a data theft or integrity issue.
Executive priority
Treat this as a targeted availability issue. It should be prioritized for storage, CI, application, or platform hosts relying on CephFS, because a local low-privilege condition can crash important systems. It is less urgent for hosts not using CephFS.
Technical view
CVE-2025-21737 is a CWE-401 memory leak in ceph_mds_auth_match()/ceph_mds_check_access(). The leak occurs when a temporary target path substring is not freed on every branch. The provided trigger condition involves CephFS subdirectory mounts and path-scoped MDS capabilities. CVSS 3.1 is 5.5, AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
Likely exposure
Exposure is likely limited to Linux hosts using the kernel CephFS client, especially subdirectory mounts with path-scoped MDS auth capabilities. The source lists Linux kernel versions including 6.10, 6.12.14, 6.13.3, and 6.14 as affected context; downstream distro status needs vendor confirmation.
Exploitation context
The bundle says the issue was detected in production through continuous memory growth, OOM, and kernel hard-lock. It is not listed in KEV, and no cited source states active exploitation. Triggering requires local access and relevant CephFS authentication and mount conditions.
Researcher notes
Evidence supports a kernel memory leak fixed in stable commits, with production impact described by the CVE text. The source bundle does not provide distro-specific fixed versions, exploit-in-the-wild evidence, or broader affected product claims. Avoid extrapolating beyond CephFS client conditions.
Mitigation direction
- Apply a vendor kernel update containing the referenced stable Ceph fixes.
- Check Linux distribution advisories for exact fixed package versions.
- Prioritize hosts mounting CephFS subdirectories with path-scoped MDS capabilities.
- Monitor affected hosts for kernel memory growth, OOM events, and hard-lock symptoms.
- Restrict unnecessary CephFS access while patching high-risk systems.
Validation and detection
- Inventory Linux hosts using the in-kernel CephFS client.
- Identify CephFS subdirectory mounts and path-scoped MDS capabilities.
- Confirm kernel packages include one of the referenced stable fixes.
- Review kernel logs for OOM or CephFS-linked memory growth.
- Validate patched hosts with normal CephFS access and memory monitoring.
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
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CWE-401: Exact CWE lookup
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Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2025-21737 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
- Medium
- CVSS
- 5.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/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:N/I:N/A:H1.83.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/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/146109fe936ac07f8f60cd6267543688985b96bcCVE reference, Linux
- https://git.kernel.org/stable/c/2b6086c5efe5c7bd6e0eb440d96c26ca0d20d9d7CVE reference, Linux
- https://git.kernel.org/stable/c/3b7d93db450e9d8ead80d75e2a303248f1528c35CVE 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.
Missing Release of Memory after Effective Lifetime
Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.