Microsoft Qlib fit Deserialization of Untrusted Data Remote Code Execution Vulnerability

April 15th, 2026
ZDI-26-274 ZDI-CAN-27211

CVE ID

CVSS Score

7.8 AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected Vendors

Microsoft

Affected Products

Qlib

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Microsoft Qlib. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

The specific flaw exists within the fit function. The issue results from the lack of proper validation of user-supplied data, which can result in deserialization of untrusted data. An attacker can leverage this vulnerability to execute code in the context of root.

Additional Details

Fixed on May 31, 2025 https://msrc.microsoft.com/update-guide/acknowledgement/online


Disclosure Timeline

  • 2025-05-22 - Vulnerability reported to vendor
  • 2026-04-15 - Coordinated public release of advisory
  • 2026-04-15 - Advisory Updated

Credit

Peter Girnus (@gothburz) of Trend Zero Day Initiative

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