dbcve.org
FreeBSDOperating system

CVE-2016-1881

HIGH · 7.8 CVSS v3.0 Published 2017-02-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The kernel in FreeBSD 9.3, 10.1, and 10.2 allows local users to cause a denial of service (crash) or potentially gain privilege via a crafted Linux compatibility layer setgroups system call.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Kernel vulnerability in FreeBSD's Linux compatibility layer (Linuxulator) allows local users to trigger a crash (DoS) or potentially escalate privileges via a malformed setgroups system call. The flaw exists in how the Linux emulation layer processes setgroups arguments, enabling exploitation by any local user with shell access.

MitigationUpdate FreeBSD to a version with the patched kernel (10.3+ or patched 9.3/10.1/10.2). If immediate patching is infeasible, disable the Linux compatibility layer (kldload linux) if not required for production operations.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FreeBSDOperating system
Affected:= 9.3= 10.1= 10.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify FreeBSD kernel version
    Run `uname -r` to display the running kernel version
    Affected if Version equals 9.3, 10.1, or 10.2 specifically (versions outside this range are not affected)
  2. Verify Linux compatibility layer module is loaded
    Run `kldstat | grep linux` to check if the linux.ko kernel module is currently loaded
    Affected if The linux.ko module appears in the output, indicating Linuxulator is active
  3. Confirm Linux emulation sysctl is enabled
    Run `sysctl compat.linux.oss` or `sysctl compat` to check if Linux system call compatibility is enabled
    Affected if compat.linux.osf1_enable or related Linux emulation sysctls are set to 1 (enabled)
  4. Check for running Linux binaries
    Inspect running processes for Linux executables (e.g., using `ps aux` and looking for Linux-branded binaries) or check /proc if linux procfs is mounted
    Affected if Linux binaries are actively executing on the system

The system is vulnerable only if running FreeBSD 9.3, 10.1, or 10.2 with the Linux compatibility layer (linux.ko) loaded and Linux emulation enabled; if Linuxulator is not loaded, the vulnerability cannot be triggered.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update FreeBSD to a version with the patched kernel (10.3+ or patched 9.3/10.1/10.2). If immediate patching is infeasible, disable the Linux compatibility layer (kldload linux) if not required for production operations.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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Scan for this in your stack

Free · runs locally
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-1881 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data