CVE-2021-37439: NCH FlexiServer v6.00 suffers from a syslog?file=/.

Q: How do I fix CVE-2021-37439?

flexiserver: upgrade to newer than 6.00. Exact commands for each OS are on this page.

Q: Is CVE-2021-37439 being exploited?

CVE-2021-37439 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-2021-37439 affect?

CVE-2021-37439 affects flexiserver. Severity is medium (CVSS 6.5). NCH FlexiServer v6.00 suffers from a syslog?file=/.. path traversal vulnerability.

Q: How urgent is CVE-2021-37439?

Priority 45/100. Public exploit reference

This month

MEDIUM 6.5UPGRADE

CVE-2021-37439 is a medium-severity flaw (CVSS 6.5) affecting flexiserver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

NCH FlexiServer v6.00 suffers from a syslog?file=/.. path traversal vulnerability.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.2% (top 31%)
CISA exploited list	No
Weakness	CWE-22
Published	2021-07-25
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: nch

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

Am I affected?

Timeline

2021-07-25 22:15 UTCPublished CVE record published
2026-06-17 04:00 UTCUpdated Record last modified

nch flexiserver UPGRADE

Affected: <= 6.00

Fixed in: newer than 6.00

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 6.00 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade flexiserver

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-2021-37439?

flexiserver: upgrade to newer than 6.00. Exact commands for each OS are on this page.

Is CVE-2021-37439 being exploited?

CVE-2021-37439 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-2021-37439 affect?

CVE-2021-37439 affects flexiserver. Severity is medium (CVSS 6.5). NCH FlexiServer v6.00 suffers from a syslog?file=/.. path traversal vulnerability.

How urgent is CVE-2021-37439?

Priority 45/100. Public exploit reference

References

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