CVE-1999-1394: BSD 4.4 based operating systems, when running at security level 1, allow the root user to clear the immutable

Routine

LOW 2.1MITIGATE

CVE-1999-1394 is a low-severity flaw (CVSS 2.1) affecting bsd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

BSD 4.4 based operating systems, when running at security level 1, allow the root user to clear the immutable and append-only flags for files by unmounting the file system and using a file system editor such as fsdb to directly modify the file through a device.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	2.1 (Low)
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Published	1999-07-02
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: bsd

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

1999-07-02 04:00 UTCPublished CVE record published
2026-06-16 21:50 UTCUpdated Record last modified

bsd bsd MITIGATE

Affected: 4.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.4

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: BSDI BSD/OS 4.0 /FreeBSD 3.2 /NetBSD 1.4 x86 / OpenBSD 2.5 - UFS Secure Level 1

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-1999-1394?

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

Is CVE-1999-1394 being exploited?

CVE-1999-1394 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-1999-1394 affect?

CVE-1999-1394 affects bsd. Severity is low (CVSS 2.1). BSD 4.4 based operating systems, when running at security level 1, allow the root user to clear the immutable and append-only flags for files by unmounting the file system and using a file system editor such as fsdb to directly modify the f

How urgent is CVE-1999-1394?

Priority 25/100. Public exploit reference

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References

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