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CVE Record

CVE-2025-21944: ksmbd: fix bug on trap in smb2_lock

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix bug on trap in smb2_lock If lock count is greater than 1, flags could be old value. It should be checked with flags of smb_lock, not flags. It will cause bug-on trap from locks_free_lock in error handling routine.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects ksmbd, the in-kernel SMB server. Under a specific SMB2 lock error path, stale flag handling can trigger a kernel BUG trap. The public sources do not provide CVSS, confirmed exploitability, or business impact beyond the kernel fix description.

Executive priority

Prioritize remediation after externally exposed or business-critical SMB services are identified. Urgency is lower than confirmed exploited kernel flaws, but kernel BUG conditions can still disrupt file-service availability.

Technical view

CVE-2025-21944 fixes smb2_lock logic in ksmbd. When lock count is greater than one, code may check an old flags value instead of the current smb_lock flags, causing a BUG trap in locks_free_lock during error handling.

Likely exposure

Exposure is most relevant to Linux systems running ksmbd on affected kernel versions or distro kernels that have not received the backported fix. Systems not using ksmbd are less likely to be exposed, based on the vulnerable component named in the source.

Exploitation context

The source bundle does not show CISA KEV listing, public exploitation, exploit code, or attacker requirements. Treat this as a kernel reliability and potential denial-of-service concern until vendor advisories provide clearer impact details.

Researcher notes

Evidence is limited to the Linux kernel fix description, stable commit references, CVE metadata, and a Debian LTS advisory. No CVSS, CWE, exploit status, or detailed attack preconditions are provided in the bundle.

Mitigation direction

  • Apply Linux stable or distribution kernel updates containing the referenced ksmbd fix.
  • Prioritize systems where ksmbd is enabled or SMB service is business-facing.
  • Review Debian LTS and other vendor advisories for package-specific fixed versions.
  • Limit ksmbd exposure to trusted networks where operationally feasible.
  • If ksmbd is unnecessary, disable it according to vendor guidance.

Validation and detection

  • Inventory Linux kernel versions and identify hosts with ksmbd enabled.
  • Compare installed kernels against vendor advisories and affected version ranges.
  • Verify the running kernel includes a backport of the referenced stable commits.
  • Check kernel logs for BUG traps involving ksmbd, smb2_lock, or locks_free_lock.
  • Confirm patched systems have rebooted into the updated kernel.
Prepared
Confidence
medium
Sources
8

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.

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CVE-2025-21944 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
1ADP providers
7Source 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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux0626e6641f6b467447c81dd7678a69c66f7746cf, 0626e6641f6b467447c81dd7678a69c66f7746cf, 0626e6641f6b467447c81dd7678a69c66f7746cf, 0626e6641f6b467447c81dd7678a69c66f7746cf, 0626e6641f6b467447c81dd7678a69c66f7746cfunaffected
LinuxLinux5.15, 0, 6.1.131, 6.6.83, 6.12.19, 6.13.7, 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.