CVE-2026-19795

Qiskit SDK is vulnerable when deserializing QPY Files and may overflow the available stack space.

Published Sep 3, 2026 CVSS 3.1 · 6.2 Medium EPSS < 1% KEV · Not listed
Description
Qiskit could allow a local attacker to cause a denial of service due to a stack overflow during deserialization of QPY payloads. A malicious QPY payload can trigger a segmentation fault, causing the application to crash when deserializing untrusted input.

Remediation

Vendor Solution

Remediation/Fixes guidance: The issue is addressed in Qiskit versions v2.5.2. This version is patched to prevent the stack overflow by no longer evaluating the expression tree for ParameterExpression objects recursively. Product(s)Version(s) number and/or range Remediation/Fix/Instructions<Qiskit SDK - qiskit.qpy.load() function>v2.5.2 Upgrade to the patched versions: qiskit v2.5.2.


Vendor Workaround

Workarounds/Mitigation guidance: None

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Description IBM Qiskit SDK 2.1.0 through 2.5.1 could allow a local attacker to cause a denial of service due to improper handling of a specially crafted object during deserialization. A malicious QPY payload can trigger a segmentation fault, causing the application to crash when deserializing untrusted input. Qiskit could allow a local attacker to cause a denial of service due to a stack overflow during deserialization of QPY payloads. A malicious QPY payload can trigger a segmentation fault, causing the application to crash when deserializing untrusted input.
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description IBM Qiskit SDK 2.1.0 through 2.5.1 could allow a local attacker to cause a denial of service due to improper handling of a specially crafted object during deserialization. A malicious QPY payload can trigger a segmentation fault, causing the application to crash when deserializing untrusted input.
Title Qiskit SDK is vulnerable when deserializing QPY Files and may overflow the available stack space.
First Time appeared Ibm
Ibm qiskit Sdk
Weaknesses CWE-502
CPEs cpe:2.3:a:ibm:qiskit_sdk:2.1.0:*:*:*:*:*:*:*
cpe:2.3:a:ibm:qiskit_sdk:2.5.1:*:*:*:*:*:*:*
Vendors & Products Ibm
Ibm qiskit Sdk
References
Metrics cvssV3_1

{'score': 6.2, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
ibm
Published
Updated
Sep 4, 2026, 8:05 PM
Reserved
Aug 13, 2026, 7:40 PM
Status
Awaiting Analysis
Published
Sep 3, 2026, 8:17 PM
Modified
Sep 8, 2026, 2:17 PM