config.py in pystemon before 2021-02-13 allows code execution via YAML deserialization because SafeLoader and safe_load are not used.

published 2021-02-14 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-13978

cvss: 9.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 2.6%; EPSS 2.6% chance of exploitation in 30 days, percentile 85%
public exploits: 0; none known

Patch / fix

fixed in 1 links 1

pystemon_project pystemon 2021-02-13

github.com/cvandeplas/pystemon@dbeb87a commit

Exploit prediction

2.61% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

huntr.dev https://www.huntr.dev/bounties/1-other-pystemon/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	7.5	AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

CWE-502 Deserialization of Untrusted Data

References

github.com /cvandeplas/pystemon/commit/dbeb87afefdb63de2f4cff69b6f10c5965d14b54
patch, third-party-advisory
huntr.dev /bounties/1-other-pystemon/
exploit, third-party-advisory

Sources

CVE List CVE-2021-27213
NVD CVE-2021-27213

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary