CVE-2021-27213: config.py in pystemon before 2021-02-13 allows code execution via YAML deserialization because SafeLoader and

Q: How do I fix CVE-2021-27213?

pystemon: upgrade to 2021-02-13. Exact commands for each OS are on this page.

Q: Is CVE-2021-27213 being exploited?

CVE-2021-27213 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-27213 affect?

CVE-2021-27213 affects pystemon. Severity is critical (CVSS 9.8). config.py in pystemon before 2021-02-13 allows code execution via YAML deserialization because SafeLoader and safe_load are not used.

Q: How urgent is CVE-2021-27213?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-27213 is a critical-severity flaw (CVSS 9.8) affecting pystemon. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.6% (top 15%)
CISA exploited list	No
Weakness	CWE-502
Published	2021-02-14
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: pystemon project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-02-14 04:15 UTCPublished CVE record published
2026-06-17 03:44 UTCUpdated Record last modified

pystemon project pystemon UPGRADE

Affected: < 2021-02-13

Fixed in: 2021-02-13

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy pystemon || rpm -q pystemon || pystemon --version

2. UPGRADE to 2021-02-13 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pystemon

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pystemon

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-27213?

pystemon: upgrade to 2021-02-13. Exact commands for each OS are on this page.

Is CVE-2021-27213 being exploited?

CVE-2021-27213 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-27213 affect?

CVE-2021-27213 affects pystemon. Severity is critical (CVSS 9.8). config.py in pystemon before 2021-02-13 allows code execution via YAML deserialization because SafeLoader and safe_load are not used.

How urgent is CVE-2021-27213?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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