CVE-2025-21647 Vulnerability Analysis & Exploit Details

CVE-2025-21647
Vulnerability Scoring

Analysis In Progress
Analysis In Progress

Attack Complexity Details

  • Attack Complexity:
    Attack Complexity Analysis In Progress
  • Attack Vector:
    Attack Vector Under Analysis
  • Privileges Required: None
    No authentication is required for exploitation.
  • Scope:
    Impact is confined to the initially vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2025-21647 Details

Status: Awaiting Analysis

Last updated: 🕐 13 Mar 2025, 13:15 UTC
Originally published on: 🕚 19 Jan 2025, 11:15 UTC

Time between publication and last update: 53 days

CVSS Release:

CVE-2025-21647 Vulnerability Summary

CVE-2025-21647: In the Linux kernel, the following vulnerability has been resolved: sched: sch_cake: add bounds checks to host bulk flow fairness counts Even though we fixed a logic error in the commit cited below, syzbot still managed to trigger an underflow of the per-host bulk flow counters, leading to an out of bounds memory access. To avoid any such logic errors causing out of bounds memory accesses, this commit factors out all accesses to the per-host bulk flow counters to a series of helpers that perform bounds-checking before any increments and decrements. This also has the benefit of improving readability by moving the conditional checks for the flow mode into these helpers, instead of having them spread out throughout the code (which was the cause of the original logic error). As part of this change, the flow quantum calculation is consolidated into a helper function, which means that the dithering applied to the ost load scaling is now applied both in the DRR rotation and when a sparse flow's quantum is first initiated. The only user-visible effect of this is that the maximum packet size that can be sent while a flow stays sparse will now vary with +/- one byte in some cases. This should not make a noticeable difference in practice, and thus it's not worth complicating the code to preserve the old behaviour.

Assessing the Risk of CVE-2025-21647

Access Complexity Graph

The exploitability of CVE-2025-21647 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2025-21647

No exploitability data is available for CVE-2025-21647.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2025-21647, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2025-21647, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: None
    CVE-2025-21647 does not compromise confidentiality.
  • Integrity: None
    CVE-2025-21647 does not impact data integrity.
  • Availability: None
    CVE-2025-21647 does not affect system availability.

Exploit Prediction Scoring System (EPSS)

The EPSS score estimates the probability that this vulnerability will be exploited in the near future.

EPSS Score: 0.044% (probability of exploit)

EPSS Percentile: 12.92% (lower percentile = lower relative risk)
This vulnerability is less risky than approximately 87.08% of others.

CVE-2025-21647 References

External References

CWE Common Weakness Enumeration

Unknown

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