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CVE Record

CVE-2025-21898: ftrace: Avoid potential division by zero in function_stat_show()

In the Linux kernel, the following vulnerability has been resolved: ftrace: Avoid potential division by zero in function_stat_show() Check whether denominator expression x * (x - 1) * 1000 mod {2^32, 2^64} produce zero and skip stddev computation in that case. For now don't care about rec->counter * rec->counter overflow because rec->time * rec->time overflow will likely happen earlier.

MediumCVSS 5.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2025-21898 is a Linux kernel availability issue in ftrace reporting. A local authenticated user may trigger a divide-by-zero condition when function statistics are displayed. The public record rates it medium, with no confidentiality or integrity impact identified.

Executive priority

Treat this as a scheduled but real availability risk. It is not presented as remotely exploitable or actively exploited, but shared Linux infrastructure with local users should be patched promptly through normal kernel maintenance.

Technical view

The flaw is CWE-369 in function_stat_show(). The kernel fix checks whether x * (x - 1) * 1000 becomes zero after 32-bit or 64-bit modulo behavior, and skips standard deviation computation in that case.

Likely exposure

Exposure is most relevant on Linux systems running affected kernel builds where local users can reach ftrace function statistics. The CVE data names Linux kernels and stable commits, but does not identify specific appliance vendors or managed service products.

Exploitation context

The CVSS vector is local, low complexity, low privileges, no user interaction, availability impact high. The source bundle says CISA KEV is false and provides no cited evidence of active exploitation.

Researcher notes

Focus validation on kernel provenance, not application packages. The vulnerable logic is in ftrace statistics display and the fix changes arithmetic handling before standard deviation calculation. Evidence does not support claims of data theft, privilege escalation, or public exploitation.

Mitigation direction

  • Apply the relevant Linux stable kernel fix or vendor kernel update.
  • For Debian LTS systems, review the cited Debian LTS advisories.
  • Prioritize shared servers where untrusted local users have accounts.
  • Check vendor guidance for distribution-specific fixed package versions.
  • Plan reboot or live-patching procedures according to existing kernel maintenance policy.

Validation and detection

  • Inventory kernel versions across Linux hosts.
  • Compare kernel builds against CVE-2025-21898 vendor guidance and stable commit references.
  • Confirm patched systems include the relevant ftrace fix.
  • Identify systems with local shell access by non-administrators.
  • Track remediation separately for Debian LTS hosts.
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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-369: 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.

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cve · low confidence lookup

CVE-2025-21898 mapping review

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Vulnerability profileCVE Program record
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

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.

1CVSS vectors
3Timeline events
2ADP providers
11Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2025-21898Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf0629ee3922f10112584b1898491fecc74d98b3b, e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d, e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d, e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d, e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d, e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d, e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d, e31f7939c1c27faa5d0e3f14519eaf7c89e8a69d, c59e74104cfd7df3ca0b5f59f1baee9c8c28b9ef, 015f0fd0fcc338513f80044add27fa46cf71d217, 1a2985af2a20b816a5cc41a2ddc1c4109ef6b9c6, 7650b4b1df091815bbbbb837d308dd4154684f8a, 010a7e846d4beaf34384c40ff18d5de10106d9b4, 5.4.9, 3.16.83, 4.4.209, 4.9.209, 4.14.163, 4.19.94unaffected
LinuxLinux5.5, 0, 5.4.291, 5.10.235, 5.15.179, 6.1.130, 6.6.81, 6.12.18, 6.13.6, 6.14affected
Weakness

CWE details

CWE-369

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

CWE-369 · source CWE mapping

Divide By Zero

Divide By Zero represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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