What is CVE-2021-23338?

CVE-2021-23338 is a medium-severity vulnerability in Microsoft Qlib, classified under Deserialization of Untrusted Data. CVSS score: 6.6/10. Published 2021-02-15.

How severe is CVE-2021-23338?

Medium severity. CVSS v3 base score is 6.6 out of 10.

Is CVE-2021-23338 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Deserialization in Microsoft Qlib

CVE-2021-23338

This affects all versions of package qlib. The workflow function in cli part of qlib was using an unsafe YAML load function.

Vulnerability class: Insecure Deserialization

Published 2021-02-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.6 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.036 (89.1th percentile), scored 2026-10-08.

Low probability of exploitation in the next 30 days, but still tracked. 89th percentile — 89.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.036 · newest: 0.036 · change: 0.000

Affected products

Microsoft Qlib
Qlib — versions 0

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

Public proof-of-concept exploits

ajmalabubakkr/CVE

References

snyk.io/vuln/SNYK-PYTHON-QLIB-1054635 (Third Party Advisory)
github.com/418sec/huntr/pull/1329 (Exploit, Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-23338?: CVE-2021-23338 is a medium-severity vulnerability in Microsoft Qlib, classified under Deserialization of Untrusted Data. CVSS score: 6.6/10. Published 2021-02-15.
How severe is CVE-2021-23338?: Medium severity. CVSS v3 base score is 6.6 out of 10.
Is CVE-2021-23338 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.