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CVE-2026-46107 dm-thin Metadata Refcount Underflow

CVE-2026-46107 is a reported vulnerability in dm-thin, leading to a metadata refcount underflow.

CVE-2026-46107 is a reported vulnerability affecting dm-thin, related to a metadata refcount underflow. The Microsoft Security Response Center published information regarding this vulnerability on 2026-05-29. Further details regarding the specific attack vector, affected products, or exploitation specifics are unavailable from the source material. However, a metadata refcount underflow could potentially lead to data corruption, system instability, or privilege escalation if successfully exploited. Defenders should monitor for suspicious activity related to dm-thin and apply available patches when released.

Attack Chain

Due to lack of specifics, a generic attack chain is provided based on typical refcount underflow exploitation:

  1. Attacker gains initial access to the system, possibly through other vulnerabilities or compromised credentials.
  2. Attacker interacts with dm-thin functionality, triggering a specific code path.
  3. The vulnerable code path contains a flaw that results in a metadata refcount being decremented below zero.
  4. The refcount underflow corrupts internal metadata structures.
  5. Subsequent operations using the corrupted metadata lead to unexpected behavior.
  6. This could manifest as data corruption, where data is written to incorrect locations.
  7. Alternatively, the corrupted metadata could lead to a denial of service.
  8. In some scenarios, the attacker may be able to leverage the corruption for privilege escalation.

Impact

Successful exploitation of a metadata refcount underflow vulnerability like CVE-2026-46107 could lead to data corruption, denial of service, or potentially privilege escalation on the affected system. Without specific details from the vendor, the precise scope and impact remain unclear. The number of potential victims and targeted sectors cannot be determined based on the available information.

Recommendation

  • Monitor systems for unusual dm-thin activity, particularly related to metadata operations.
  • Deploy the Sigma rules provided to detect potential exploitation attempts (see below).
  • Apply patches released by Microsoft to address CVE-2026-46107 when available.
  • Investigate any alerts triggered by the provided Sigma rules in your environment.
  • Enable relevant logging for dm-thin related events to facilitate investigations.

Detection coverage 2

Detect CVE-2026-46107 Exploitation Attempt - Suspicious dmsetup Usage

medium

Detects CVE-2026-46107 exploitation attempt by monitoring for suspicious dmsetup commands that may indicate attempts to manipulate dm-thin metadata.

sigma tactics: defense_evasion techniques: T1562.001 sources: process_creation, linux

Detect CVE-2026-46107 Exploitation Attempt - Monitoring for specific dm-thin kernel messages.

high

Detects CVE-2026-46107 exploitation attempt by monitoring for specific dm-thin kernel messages.

sigma tactics: defense_evasion techniques: T1562.001 sources: kernel, linux

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