# CVE-2026-116500: Unbound Recursion in QPY deserialization can lead to denial of service

Status: published. Published: 2026-11-08. Updated: 2026-11-08.

IBM Qiskit SDK 2.4.0 through 2.6.1 could allow a local attacker to cause a denial of service due to unbound recursion during deserialization of untrusted QPY payloads.

## Remediation

- fix: Remediation/Fixes guidance:



The issue is addressed in Qiskit versions v2.6.2.



Product(s)Version(s) number and/or range Remediation/Fix/Instructions< Qiskit SDK https://github.com/qiskit/qiskit  - qiskit.qpy.load() function>v2.6.2

Upgrade to the patched versions: qiskit v2.6.2. (source: CNA: ibm)
- workaround: Workarounds/Mitigation guidance:




None (source: CNA: ibm)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: ibm) — https://www.ibm.com/support/pages/node/7295235

## Affected products and versions

- IBM / Qiskit SDK: ≥ 2.4.0; ≤ 2.6.1 (affected, semver). Source: CNA: ibm

## Severity and prioritization

- CVSS 3.1: 6.2 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: ibm

- CVSS 3.1: 6.2 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: psirt@us.ibm.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-502

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://www.ibm.com/support/pages/node/7295235 (CNA: ibm; vendor-advisory, patch)

- https://www.ibm.com/support/pages/node/7295235 (psirt@us.ibm.com)

## Provenance

- CNA: ibm: https://www.cve.org/CVERecord?id=CVE-2026-116500; retrieved 2026-11-08; source updated 2026-11-08

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116500; retrieved 2026-11-08; source updated 2026-11-08

Revision: 27f47643e1e818bd2ac621bc2ec3a9ab850f03c258e511bc2e1a3496ab499a3f

Canonical: https://y2.dev/cve/CVE-2026-116500

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