dbcve.org
FreeBSDOperating system

CVE-1999-0305

MEDIUM · 5.0 CVSS v2.0 Published 1998-02-01
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
59/100
Remediation priority · Elevated
Remotely reachable No privileges 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 system configuration control (sysctl) facility in BSD based operating systems OpenBSD 2.2 and earlier, and FreeBSD 2.2.5 and earlier, does not properly restrict source routed packets even when the (1) dosourceroute or (2) forwarding variables are set, which allows remote attackers to spoof TCP connections.

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

The sysctl facility in OpenBSD 2.2 and earlier and FreeBSD 2.2.5 and earlier fails to properly restrict IP source-routed packets, even when the dosourceroute or forwarding sysctl variables are configured to block them. This allows remote attackers to inject spoofed TCP packets by specifying arbitrary source routes, potentially enabling TCP connection hijacking or session impersonation.

MitigationConfigure kernel parameters to disable IP source routing (set net.inet.ip.sourceroute to 0 or equivalent), and consider filtering source-routed packets at network perimeter devices. For legacy systems, apply historical patches from OpenBSD and FreeBSD archives.

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:= 2.2= 2.2.5
Bsd OsOperating system
Affected:all versions
OpenBSDOperating system
Affected:= 2.0= 2.1= 2.2

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
Network
Complexity
Low
Authentication
None
Confidentiality
Partial
Integrity
None
Availability
None

AV:N/AC:L/Au:N/C:P/I:N/A:N

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 the operating system and version
    Run 'uname -a' or check /proc/version (Linux) or 'oslevel' (AIX) or 'sw_vers' (macOS) to determine OS type and version number
    Affected if The system is running FreeBSD 2.2-2.2.5, OpenBSD 2.0-2.2, or Bsdi Bsd Os any version
  2. Check sysctl value for IP source routing
    Run 'sysctl net.inet.ip.sourceroute' on FreeBSD/OpenBSD, or 'sysctl -a | grep source' on Linux to see if source routing is enabled or disabled
    Affected if The sysctl variable exists and shows source routing is permitted (value 1 or not explicitly set to 0)
  3. Verify the dosourceroute sysctl setting
    Run 'sysctl net.inet.ip.dosourceroute' or check the equivalent sysctl parameter for source route blocking
    Affected if The dosourceroute variable is set to allow (value 1) or the variable does not exist on the system
  4. Check if IP forwarding is enabled
    Run 'sysctl net.inet.ip.forwarding' or 'sysctl net.ipv4.ip_forward' to check if packet forwarding is enabled
    Affected if IP forwarding is enabled (value 1) which may allow source-routed packets to be processed
  5. Review network configuration for source route acceptance
    Check network configuration files or run 'ifconfig -a' and review any firewall rules that may accept or reject source-routed packets
    Affected if Network filters are not explicitly blocking IP source-routed packets

A system is affected if it runs one of the vulnerable versions (FreeBSD 2.2-2.2.5, OpenBSD 2.0-2.2, or Bsdi Bsd Os) AND IP source routing is not disabled at both the sysctl level and network filtering level.

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

Configure kernel parameters to disable IP source routing (set net.inet.ip.sourceroute to 0 or equivalent), and consider filtering source-routed packets at network perimeter devices. For legacy systems, apply historical patches from OpenBSD and FreeBSD archives.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-1999-0305 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
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