Executive brief
Qiskit SDK is a quantum computing library used by researchers and developers to design and simulate quantum circuits. A flaw in how the library processes QPY (Qiskit Pickle YAML) files allows an attacker to craft a malicious file that causes the application to crash when loaded, disrupting work and potentially impacting dependent systems or services.
Technical details
The vulnerability exists in the deserialization logic of qiskit.qpy.load(), which recursively evaluates ParameterExpression objects in QPY payloads without proper depth limits. An attacker can craft a specially constructed QPY file with deeply nested ParameterExpression objects that triggers excessive recursion, overflowing the stack and causing a segmentation fault. The attack requires local file access or the ability to supply untrusted QPY input to the application; no authentication or user interaction is required once the malicious file is processed. The impact is denial of service through application crash. IBM patched this in Qiskit v2.5.2 by eliminating the recursive evaluation of the expression tree; versions 2.1.0 through 2.5.1 are affected.
Affected products
- IBM Qiskit SDK 2.1.0 through 2.5.1
Timeline
- 2026-09-03: disclosed
- 2026-09-03: patched: Fixed in Qiskit v2.5.2