CVE-2021-39274: In XeroSecurity Sn1per 9.0 (free version), insecure directory permissions (0777) are set during installation,

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-39274 is a critical-severity flaw (CVSS 9.8) affecting sn1per. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In XeroSecurity Sn1per 9.0 (free version), insecure directory permissions (0777) are set during installation, allowing an unprivileged user to modify the main application and the application configuration file. This results in arbitrary code execution with root privileges.

Why this priority

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

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.1% (top 12%)
CISA exploited list	No
Weakness	CWE-276
Published	2021-08-19
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: xerosecurity

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

Am I affected?

Timeline

2021-08-19 12:15 UTCPublished CVE record published
2026-06-17 04:03 UTCUpdated Record last modified

xerosecurity sn1per DOWNGRADE

Affected: 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

1. Check installed version

apt-cache policy sn1per || rpm -q sn1per || sn1per --version

2. No fixed release: DOWNGRADE to a release before 9.0 (Debian / Ubuntu)

apt-cache madison sn1per sudo apt install sn1per=<VERSION_BEFORE_9.0> sudo apt-mark hold sn1per

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list sn1per sudo dnf downgrade sn1per-<VERSION_BEFORE_9.0> sudo dnf versionlock add sn1per

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2021-39274?

sn1per: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-39274 being exploited?

CVE-2021-39274 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-2021-39274 affect?

CVE-2021-39274 affects sn1per. Severity is critical (CVSS 9.8). In XeroSecurity Sn1per 9.0 (free version), insecure directory permissions (0777) are set during installation, allowing an unprivileged user to modify the main application and the application configuration file. This results in arbitrary cod

How urgent is CVE-2021-39274?

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

Related CVEs

CVE-2021-39273 HIGH 8.8 DOWNGRADE In XeroSecurity Sn1per 9.0 (free version), insecure permissions (0777) are set upon application execution, all

References

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