CVE-2025-40209 Vulnerability Analysis & Exploit Details

CVE-2025-40209
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-2025-40209 Details

Status: Received on 21 Nov 2025, 11:15 UTC

Published on: 21 Nov 2025, 11:15 UTC

CVSS Release:

CVE-2025-40209 Vulnerability Summary

CVE-2025-40209: In the Linux kernel, the following vulnerability has been resolved: btrfs: fix memory leak of qgroup_list in btrfs_add_qgroup_relation When btrfs_add_qgroup_relation() is called with invalid qgroup levels (src >= dst), the function returns -EINVAL directly without freeing the preallocated qgroup_list structure passed by the caller. This causes a memory leak because the caller unconditionally sets the pointer to NULL after the call, preventing any cleanup. The issue occurs because the level validation check happens before the mutex is acquired and before any error handling path that would free the prealloc pointer. On this early return, the cleanup code at the 'out' label (which includes kfree(prealloc)) is never reached. In btrfs_ioctl_qgroup_assign(), the code pattern is: prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL); ret = btrfs_add_qgroup_relation(trans, sa->src, sa->dst, prealloc); prealloc = NULL; // Always set to NULL regardless of return value ... kfree(prealloc); // This becomes kfree(NULL), does nothing When the level check fails, 'prealloc' is never freed by either the callee or the caller, resulting in a 64-byte memory leak per failed operation. This can be triggered repeatedly by an unprivileged user with access to a writable btrfs mount, potentially exhausting kernel memory. Fix this by freeing prealloc before the early return, ensuring prealloc is always freed on all error paths.

Assessing the Risk of CVE-2025-40209

Access Complexity Graph

The exploitability of CVE-2025-40209 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-2025-40209

No exploitability data is available for CVE-2025-40209.

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-2025-40209, 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-2025-40209, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: None
    CVE-2025-40209 does not compromise confidentiality.
  • Integrity: None
    CVE-2025-40209 does not impact data integrity.
  • Availability: None
    CVE-2025-40209 does not affect system availability.

CVE-2025-40209 References

External References

CWE Common Weakness Enumeration

Unknown

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