What is CVE-2021-28667?

CVE-2021-28667 is a high-severity vulnerability in Python, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2021-03-18.

How severe is CVE-2021-28667?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Python

CVE-2021-28667

StackStorm before 3.4.1, in some situations, has an infinite loop that consumes all available memory and disk space. This can occur if Python 3.x is used, the locale is not utf-8, and there is an attempt to log Unicode data (from an action or rule name).

Published 2021-03-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.022 (82.1th percentile), scored 2026-10-01.

Low probability of exploitation in the next 30 days, but still tracked. 82nd percentile — 82.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.022 · newest: 0.022 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-835 — Loop with Unreachable Exit Condition (Infinite Loop)

References

stackstorm.com/2021/03/10/stackstorm-v3-4-1-security-fix/ (Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-28667?: CVE-2021-28667 is a high-severity vulnerability in Python, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2021-03-18.
How severe is CVE-2021-28667?: High severity. CVSS v3 base score is 7.5 out of 10.